No age limit....it’s a health limit.
Went out with a nice group of disabled veterans one time (Soldiers Undertaking Disabled Scuba)
We pulled up on the wreck and a 73 year old Nam vet grabbed the 20 pound anchor and jumped over and rode it down and tied us into the wreck 115 feet below.
As long as you are physically fit and healthy, there isn’t an "age limit".
I guess I went thru "middle age crisis" a few years ago. When I turned 40 I quit diving and sold all my gear. Didn’t dive for about 5 years because I was "too old". Finally couldn’t stand it anymore so I bought all new gear (again) and started diving again. Now I’m 50.