One of the first recipes I put together myself, for my second AG batch, was based loosely on an altbier (without really knowing what an alt was). It came out, meh... OK. Not terrible, but a bit too harsh. Couldn't pick up the malt flavor from the 2-3 lbs of Munich malt I used. Too many hops. Not bad, it was drinkable, just medicore.
Fast-forward about six or seven months, to a couple of weeks ago. I'm going through the stashes, seeing what I have for brews, just doing a bit of an inventory. I find a couple cases of these and toss a couple bottles in the fridge. Low and behold, a lot of the bitterness seems to have dropped out, along with almost all of the excessive hop flavor. The malt is shining through, full and sweet. It's got a great balance, it's not too bitter, it's not too hoppy, and it's not too malty. It just came out really, really good (especially if drunk a little on the warm side), a HUGE improvement over the "meh" batch I had on my hands when I first bottled it.
I have an ESB in the keg that I was very disappointed in. At first, it was real fruity, then it seemed to get harsh on me (which was odd). I haven't touched it in a couple months, but I'm going to pull a pint tonight and see what I have. It's probably pushing six months old now, which is a while for an ESB, but I'm hoping that it's mellowed out and become a smoother, maltier brew now as well.
The only truly BAD batches I've had have not improved, but those were issues more to do with me not knowing how to formulate a recipe or using too much fruit in too small a beer - mocha stouts with far too much chocolate and coffee never really get any better
