I have a few comments on this subject. My other hobby is cycling, and I put on a ton of miles and work very hard at getting faster etc. On one hand, I have a lot more energy through the day, and I am certain that it translates to my health on the kit. I'm older like you, my avatar mercifully doesn't show all the gray.
On the other hand, I've learned a lot about training the body to do specific things, like playing the drums for long periods of time or climbing hills on the bike. The most important thing I've learned is specificity. It means that to build the strength and endurance to do a thing well, you must do the thing. If you want to climb hills, you don't do it in the weight room, you do it on the hills. If you need endurance on the kit, play more. If you're dragging after 45 minutes of playing, start practicing in 90 minute chunks of steady work. Jogging or cycling will massively improve your body's aerobic system, but you need lots of kit time to keep your feet, wrists and fingers supple and responsive.
And I'm going to guess you are a much better drummer than you think you are, that your many years gives you fine tuning that you can't get any other way. We don't all have to sound like Dave, Vinnie or Jo Jo with dizzying wow factor. Maybe assessing your current band and deciding what it needs to become would be best. Don't be too hesitant to approach the subject with your band, you're probably not the only one who would like more fulfillment. I don't think you're too old to play, but I do think you're too old and wise to play in a project that doesn't get you excited.
G/L!
John