Yes, i do, especially with RB's, who have a much shorter shelf life than other skill positions. For example, Stephen Jackson is younger than DeAngelo Williams, and SJax was drafted two years before him. Clinton Portis is two years younger than LJ, and was drafted the year before. When RB's start bucking 30, that is a BIG difference. For someone not to take something like that into account is not being as thorough as they should be.
Are you so sure that it's age that causes the decline in RBs, and not workload? Personally, I believe the reason RBs over 30 fall apart is because by the time they turn 30, they've accumulated a TON of wear and tear- not because there's some magical switch that their body turns on when they turn 30 that makes them more susceptible to injury or decline.
I think they are both factors, but i think it is more age than anything else. Also, as people get older, they are certainly more susceptible to injuries. You can test this theory if you like, go knock down a ten year old girl, then knock down your grandmother, whom do you think is the more likely candidate for hip replacement surgery?
You're talking about a difference of 60 years. I'm talking about a difference of 2 years- the difference between 28-year-old RBs (who are in their prime), and 30-year-old RBs (who are "an injury waiting to happen). That's literally the perception- Tomlinson, who is 28, is considered "in his prime", but if he were 30, he'd be a walking red flag. This cannot be explained by the gradual and slow effects of aging on the body's regenerative processes (the biggest losses in that department occur earlier than age 30, anyway). The only theory, in my opinion, that really fits that mindset is the "magical lightswitch" theory.