Lots of people are treating this like you would go back in time and get a do over, rather than being de-aged.

I'm assuming that de-aging would roll back any age related aches and pains, but not affect my memory, other than possibly making it better. It would give me more energy, so I'd be overweight and young instead of overweight and old :D

I'd take it at around my late 30s to early 40s to get back to my late teens to early 20s. My body was fully developed, so I wouldn't have to go through puberty or have too many teenage hormones, and I'd have enough energy to get in shape again.

If it de-aged me by putting me back into my body from the time, then it would be when I was 42. 22 was when I was in the best shape of my life, and before I picked up a few long lasting injuries. I found out in my early 30s that I've got a chronic illness too, and it hit me hard.

I'd get the doctors and dentist to work on the health issues that I didn't know about when I was young, and stop them from becoming serious, and generally get healthier.

Most importantly, I'd take my kid out and do all the things that we haven't been able to do together :)