"I did read a couple of threads here that basically said that if you are over 40, don't bother. I don't buy that."
Oh yeah, the Young And The Arrogant are always ready to tell us old fogeys that since we're 3/4 dead already, we may as well just give up and make room for Generation X or Z or K or whatever. I said the same crap when I was young and stupid, ignoring the evidence of people like my grandfather. In his '70s, he worked construction with my Dad just for something to do in his retirement, and he worked as hard or harder than guys one third his age. In the evenings he played drums with a jazz trio at a local bar. He even went home with one of the bar maids once in a while (you can't keep a secret in a small town), and this was before Viagra.
Drothen, you get out there and do what you feel driven to do, and ignore the Young And The Arrogant. Do your Tai Chi Chuan classes or whatever. I'd also suggest talking to pistolcraft/CQB instructors about tactics for those of diminished mobility. If you learn any good tips share them; I'm only 5 years behind you.