Part of the enigma of wine -- not to mention frustration and fascination -- is the way in which it ages. And predicting how a given wine will age is a precarious business. How can someone so surely predict that a wine without any sort of track record, barely past its first vintage, will last another 25 years? (As an example, take Robert Parker commentating on the future of the Fox Creek Reserve Shiraz 1996 from South Australia.) Surely even the winemaker would struggle to make such a bold prediction (or at least keep a straight face in the process)? I personally feel any super-ripe, high alcohol and acid-adjusted wine like this will struggle to maintain much of a drinking cycle at all, but there again I'm not that enthused with it from the start. But even if I'm not right in this case, I'll no doubt be proved right on other occasions when more lauded critics will get it wrong -- such is the difficulty in predicting how wine will age.

The frustration with the unpredictability of the ageing process is offset by the joy provided by sublime examples of older wines, which at their peak can scale such heights that younger examples just can't compare. I'm thinking particularly of recent experiences I have had with a 1959 Leoville Barton and a 1975 Tempier Bandol -- two wines elevated by age to enthralling heights that eclipse the pleasure given by younger examples.

But what a risky game it is we play! Just how much wine is saved back only for it to decline in the bottle? How many red faces will the critics endure in making predictions designed to help their readers, when in fact we know very little about the ageing process of wine, let alone provide a basis for sure-fire predictions.

I personally think a wine's track record over previous years, given roughly similar vintage conditions and resulting wine style will generally provide the best predictor. Beyond that, the structure and balance of a young wine will provide some clues as to its likely evolution, but these clues will only as good as the taster's ability to distinguish these components. Such is the winemaking skill in helping wines show well in their youth, that nowadays it's a tricky game: oak and chemical manipulations can hide flaws which will only become apparent with a little more time in the bottle.

Some will imply (e.g. Parker) or even say outright (Vic Williams, an NZ wine critic) that the way in which a wine holds or even improves once opened provides a good clue as to its ageing potential. I'd certainly treat this ability as a positive indicator. Others will say it proves nothing beyond how a wine behaves once opened, as we are subjecting the wine to oxidative ageing and in the bottle, reductive ageing -- its polar opposite -- is actually occurring. But, given the way in which cork doesn't always provide a perfect seal, I can see how some of the wine's development may come from a bit of oxidation, or at least how some wines will survive poorer corks better than others.

Over the years I've experienced many examples of wines drunk over long hours or even the next day, as a full bottle is too much for even the two of us on a weekday evening. I also don't often wish to defer wine enjoyment just because I haven't got a willing partner to share the rest of the bottle! As I write, I'm seeing in the start of the year with a Leoville-Barton 1990, a bottle I actually opened last year (call it yesterday if you must)! But how come I'd risk an expensive bottle that may become undrinkable the next day? Well, at the same time I drunk the 1959 example I gave above, I drunk the 1990, and thought it and the '86 where the recent vintages of Leoville-Barton most likely to have 30 more years of longevity. Not only that, I've previously had excellent experience of drinking young Bordeaux over two days. Often its tannic edge is rounded off and in this case this is exactly what happened. I loved the cigar boxy character the 1990 displayed when first opened (which has now sadly gone) but in place of its more oaky profile and tannic finish is a fruitier, richer-tasting example which is rounded off nicely with a long fruity finish. A slightly different wine from yesterday, not better in all departments (loss of complexity is often the first negative change when early oxidation takes over), but certainly its equal overall. But what gives me the best hope of this wine lasting 30 more years? The way in which it held up over 24 hours or the way in which the '59 tasted? I have to say it's the track record of Leoville-Barton as an estate, as well as the fact that it comes from a year which has a firm finish (unlike the softer, shorter 1982, for example), not the way it holds up overnight. I'd like to think that had it degraded drastically overnight, I'd still have faith in the wine being one for long ageing, although this faith may have been somewhat shaken.

On a slightly controversial note, I've recently concluded that of all wines, Champagne survives the best once opened and left overnight, tasting practically as fresh as when it was opened the first day, overnight! Take a quality champagne, exercise care when pouring out half a bottle, and with firm re-corking and an overnight stay in the fridge, you'd be hard pushed to even notice a loss of carbon dioxide let alone flavour. (I wouldn't recommend this with less than half a bottle left, though.) My belief is the carbon-dioxide layer acts as a preservative, and this could offer an explanation for the popular 'myth' that a silver spoon placed in the neck will keep Champagne fresh (albeit the spoon probably does nothing at all, or perhaps at most, helps trap the carbon dioxide).

Weirder still was the occasion when I recently opened a young Mersault which had an unpleasant maderized edge to it. Declaring it dead, I didn't throw it away, thinking I could cook with it. But, the next day, as strange as it seems, the wine tasted much fresher than before! How can this be, given that maderization is a function of oxygen exposure, and if anything have been speeded up by the wines being left overnight. But then take the example of Château Musar, a wine which often exhibits volatile acidity and oxidative notes when young only to seem younger and fruitier as it ages! Nothing is quite as it seems when it comes to wine ageing.

One of my favourite wines from Australia is Jim Barry's The Armagh Shiraz, a wine I know that ages well (in fact some might say frustratingly slowly). Imagine my disappointment and surprise when I thought I was safe in drinking the 1995 over two days only for it to be marred by volatile acidity after being left overnight. What does that tell us about a wines ageing potential? Hopefully nothing other than its susceptibility to bacterial spoilage. But then perhaps this wine is also vulnerable in the bottle too? Time will tell.

So, although some age-worthy wines can survive overnight without becoming a lesser experience, others can't. And there are plenty of simpler, lesser wines with limited ageing potential that will be fine left overnight. (As an aside, I often put them in a fridge to slow down oxidation, but overall there seems to be no advantage of one method of overnight storage over any another. I used to decant to half bottles if I wanted to split a wine over two nights, but now I don't bother, as it doesn't seem to be better: the pouring process itself is a sure fire way to introduce a massive amount of oxygen to a wine.)

But what about ageing a wine with a view to seeing it improve? Again, there's no hard science here, just anecdotal examples. On more that one occasion have I experienced wine which has not had ideal storage but actually provided a more interesting drink than one that did. I know Jamie Goode stored his bottles of Jaboulet Crozes-Hermitage Thalabert 1990 at home and delicious, complex drinks they where too, but ones which show limited potential for any further improvement. However, I recently purchased bottles from what must have been cooler storage only to find they where so youthful in comparison -- they've had more in common with the '95 vintage bottles I've drunk to date! I have to be honest and admit Jamie's bottles had become more complex and interesting faster than other bottles might but given the circumstances this was no bad thing! My first bottle went on to drink well over two days, which gives me the confidence to expect they too will become more complex, but then who can be really certain?

I've had wines which some criticise for being too soft and lacking structure (e.g. Clive Coates on the Caurrades de Lafite '96), only to find that they go on to drink well, tasting richer and fuller, over two days. This gives me the confidence to ignore critical notes and expect a wine to go on to provide years of pleasure, perhaps even greater pleasure in time. However, I've also found others that have been predicted to have a long future (e.g. Parker on the Pontesac '96), only for them to show poorly the next day. (I still expect this wine to last 10 years -- but maybe now I've got less confidence in it's ability to improve dramatically.) However, above all, what really counts is experience. I've tried to age many New World wines simply to be disappointed. Therefore, even an overnight improvement may not give me the confidence to think a New World wine will improve, and I sometimes even think a wine might actually show best while young after plenty of air rather than actually improve with ageing. (I'm especially thinking here of young oakier wines in which air seems to bring about better balance, yet the wine as it ages becomes even more oak dominant as the fruit fades.)