I'm in my mid thirties, do not take any medication, nor never had any equipment problems except for once. (Well other than finishing on queue). When I was in my late teens, I busted my bulbourethral artery due to too much activity. I was doing it about 4-8 times a day with multiple girlfriends, pretty much 7 days a week, not counting manual stimulation.
Even before that traumatic event, I had difficulty finishing below 30 minutes of continuous activity. Even manual stimulation becomes a chore, on occasion. Once you factor in the small talk, shower, and/or foreplay, in a one hour session, if I pop just once I consider it a success. Does not mean there is anything wrong with my partner (for the past few decades, I've been honored to have met some truly exquisite creatures). There is no major stress in my life, usually the only thing on my mind is the activity at hand.
Over the years, I have learned to book multi hour sessions (if I want to pop more than once, which I'll admit sometimes I don't) and just go with the flow. Accepting the fact, that the finish line might be well beyond my reach, has allowed me to slow down my rhythm and just enjoy the race.