Welcome the club. I also have both, plus Ledderhose. Like you, things started to progress after 40, but I'm now 57 and all three conditions are what I'd call "manageable".

Yes, these conditions are statistically associated with aging. Don't let it panic you though. Progression is unpredictable, can stop for long periods. The symptoms may be noticeable, but may not cause functional problems. There's just no way to predict.

Treatment options are improving all the time. Xiaflex is now in trials for Peyronie's as well as Dupuytren's. For hand/finger contractures, NA is still the best choice.

Now the bad news. I've had surgery on both hands and while I'm ok for everyday activities, playing a stringed instrument wouldn't be possible (I used to play guitar and bass). Surgery has variable results and usually causes some damage. So, don't get talked into surgery until you're at the end of your rope and have exhausted all the other alternatives. Even then, ask yourself if you couldn't wait a few years to see if treament improves.

If you do need surgery, find an 'ace' hand surgeon who understands the dexterity required to play an instrument.