I can't agree more with your statement of how keeping active allows you to have a much younger body than others of the same age. I run with a few guys who look 10-15 years younger than they really are, and more importantly they live like they are 10-15 years younger. While their peers may be complaining about different pains and struggling to get out of bed etc., these guys are able to go run for 10K-20K at a time and still have a social life like everyone else around!