Sure, people get older and weaker, but you always see the sensei (sp?) like splinter in ninja turtles, the karate kid's teacher, as well as just about every other movie that has a 'teacher' involved, that he is old, gray haired, weaker, but he knows where to hit to make them stay down and none messes with them.
With age, have some sort of battle wisdom come. Fine, don't give warriors +5 str/dex/con, keep taking away the points, but give them some sort of fighting finnesse (sorry to overlap the name of swashi skill).
Or...
We could always just go for the second idea. Skills based on age, rogue get some sort of uber hide (as in hiding not in skin). Sorcs a glorified scribe/recharge, priests a better brew, swashi a more bitting taunt.
Eh, just rambling though, I guess I'm just starting to get bored and want a new skill to play and brag about