Sexual performance is actually a very, very good marker of overall health. If you want to perform better, the only real way is to take care of yourself. That's hydration, eating clean, laying off the sauce, getting good sleep, exercise (including kegels), maintaining a healthy weight, etc.
I know that's a tall order just for an additional pop, but, health pays dividends.
Personally, my current record is 5 in a couple hours. Probably could have done more, but, I was pretty gassed after that and needed a break. The secret to that is to have really good pelvic floor muscles and understand how to use them, then when you get pushed over the edge, hold your breath and clamp down hard, stop all stimulation, and then relax as you take a breath. You get a 75% orgasm out of the deal, but, no refractory period so you can get right back to it in like 10 seconds.
TL;DR; If you want to fuck like you're 20, you need to be healthy like when you were 20.