Speaking from experience anyone in their 50s, provided they are still in good health, is probably a better bet in terms of drive and commitment, than most past their early 20s.
I'm in my 50s and the rest of my band are half my age, but I have noticed a drop off in interest on the part of some previous members as they start looking at settling down, buying a house and having kids, building a career etc. That's nearly all behind me, so I have plenty of time to devote to music and IMO the fact that I'm still writing songs and play should say it all. I know my current band appreciate that.