I think the ability to learn "new tricks" has very little to do with age and everything to do with attitude. I've met many young "pups" who already think they know it all at age 22 and won't listen to anyone's advice. Some may wisen up over the years and learn to heed the wisdom of others... but in my experience most know-it-all's have a very hard time realizing they are not, in fact, the central hub of the collective knowledge of the universe.
Personally, I believe I can learn something new from anyone, no matter their age, social standing, background, etc. In fact the more they differ from me, the more I can learn from them, and the more curious I am about them. Unfortunately, I have met few people who seem to share this viewpoint and apply it daily.