Calf Longevity Tips?

I'm not teenager young anymore but still very in shape and have always been "athletic." My game is modeled after Dennis Rodman - getting every rebound and always jumping higher and having more energy than everyone else.

Unfortunately, I can't seem to play two days in a row anymore. I can play for 3 hours straight one day, and the next day I can't even hoop by myself because I get extreme calf muscle pain to the point where I'm limping off the court after lightly jumping around for 20-30 minutes. Totally equal pain/tightness in both calves, no issues in my upper legs.

I don't even know where to start or if I'm just getting old. I am very flexible and stretch a lot before playing, and try to do things in the gym to strengthen my legs.