Where I do agree that many beers improve with age, it is very recipe dependent. And depending on which characteristics you were really shooting for in that particular recipe, the time frame that this will occur can vary dramatically. Like, for instance I had a NutBrown Ale that tasted not all that great up to oh I dunno, like 1.5 months post bottle, but then it magically went through this 'window' for like a month where it was really good. Then it turned, although it didn't get 'bad' it just lost the magic. My house ale recipe is like a Chameleon, no kidding. It seems to constantly morph in the early 2 months, I personally felt it was at its best at 3 months and didn't improve after that.
I need to take notes. It's all in my head now, but I think I should become more serious on writing down time frames as I think it is absolutely key. So what I am getting at is, I believe every beer has its own 'magical window' where it may peak then fall off, or may peak and not improve at all after that point. Or it may just keep morphing if you keep it around long enough.
This is coming from the strict bottle conditioned viewpoint.