@calitennis127, that was an odd response above - because you complained about me "stretching the significant of a just a few points" and then did just exactly that. As
@Federberg pointed out.
Further, I am not making "wildly exaggerated conclusions." The numbers don't lie: Roger was at his best in 2004-07, with 2006 being his best overall year, and a significant dip in 2008. You can see this on the surface, but also by digging deeper. Does anyone other than you disagree with that?
This doesn't mean that he hasn't been able to play brilliant tennis since then - we've all seen it, especially over the last year or so. But the point is that when he was 24-25 he was able to find his best more consistently.
Or we can look at Rafa. Still a great player, still capable of demolishing an opponent on clay or hitting a ridiculous down-the-line forehand. But is he as consistently great as he was in 2008-2013? No way.
Remember when you were 25 and you could pretty much eat or drink anything you want, and be no worse for wear for it? Not so much the case at 35, or even 30. The body changes - it doesn't bounce back as quickly, and requires more care. It doesn't mean that a 35 year old cannot be fit or perform at a high level, but that the window narrows.