As someone in their mid-30s ...
Here are some major factors ...
1. Your heart
The muscles, longevity and control in your penis is related to your cardio-vascular. Make sure you are active and healthy. This includes weight that puts a burden on your heart.
2. You're not young any more
It's probably related to #1 as well, but you're not young any more. You can't jack ejaculate with a complete and utter hard-on any more several times a day. You have to "work" at doing such, and it might go soft at times. Work it into your routine, and "save up" for that every 2-3 day sexual blast.
3. Forget the movies, studs love 100%, not ram 100%
Forget the movies and discover that love making is not about raming her hard.** It's about the emotional connection and enjoyment. Yeah, some women might want that one night stud, and they won't go for it. But it
never hurts to "fill your time" by
focusing on her.
Nothing gets me harder than eating my wife out and hearing her react. But even before that, a good 5-10 minutes of just kissing to start really works as well. And that's
not where we are kissing and "heavy petting," but the "initial engagement."
Tease your cock. Make it beg you for it. Make it beg you to go farther. Be that teenager (or pre-teen if that's the case) that used to wish to go past 1st, 2nd and 3rd base, and limit yourself. Anticipation is where it is at, honestly, it
has to become mental to "keep it going strong."
In all honesty, this is why as you age, it's nice to have a lover who understand why you're not the "teenage stud" you used to be. If you're lucky, like me, you have this same woman since she was a teenager, and you get to experience all of her changes over her life.
**NOTE: One thing I've found is that it seems to be the opposite for women. The younger they are, the more "tender" they really like it (despite "popular attitudes"). The older they are, the more they are "open" and then like to be "rammed" at times. As I regular joke, half-serious, older women should date young studs where it won't go down, and older men should date young girls that want lasting, tender love making sessions.
Also, one more thing that effects me, or anyone else who often takes "cold morning showers." Although the "hot bath" does really help, even those of you that take very hot showers ...
A. Body temperature
I find that by taking cold showers, I reduce my internal body temperature by 1 full degree Celsius (1.8 F), which helps living in the southern US for 8-9 months of the year. But I also find my sexual drive goes down, heavily. Consider taking an extended, hot baths a few hours before going out. About the only negative is that your sperm count will be down (but don't treat that like a contraceptive, it is
not).