I've only managed to get 2 pops in bookings that are at least 1.5 hours long but it's not guaranteed.
Until last year I thought I was only ever a 1 pop guy, in fact I never even tried to go for a 2nd round but that all changed when I went to see smiley sindy. I popped so early in my booking with her after some great oral & after a few minutes rest she was determined to get me to pop again, which to my surprise she managed.
I use cialis & this definitely helps getting me up for round 2 but it's definitely a lot of hard work to cum again & success really depends on how I'm feeling on the day.
I agree that looking after yourself health wise definitely helps performance.