Age beer? Does beer age in the bottle like wine?
Per others, it does vary and some don't need to age. All beer ages a bit in cask/tank. Finer beers and mainly higher gravity ones will benefit the most in general (some lambics and gueze too). Many are also blends where part is aged for some period in oak, sherry casks, etc.
As far as post bottling, the same is probably true in general and more so for those with live yeast, on lees, etc.
I never seem to hold on very long, but have aged a few and they did mellow a bit like a burgundy.
scaldis noel for 3 years.
Abbey de floreffe (magnum bottle) for 2.
I guess that is why they call them the burgundies of Belgium.
I've had less success in holding on to barley wines, scotch ales, and other misc higher gravity examples, etc. cause I like em, but I've had a decade of Thomas HArdy's (every other 2 years), and 5 straight years of Anchor (special holiday beer a few years ago).
fullers 1845 and their vintage series will age for a while and do taste better over time. (I can never seem to hold on to these very long either.)
Most commercially available in the US probably won't hold up well to aging for a decade, but I am sure there are some examples in Europe where you can find exmaples 10+ years old, or special blends where one of the additives is 5, 10, etc. years old. I've never tried these, but had a friend in the business that was treated to examples at cloisters on a buying trip.