Ah, I dream of the days when premature ejaculation was a problem. Nowadays, I have to beat the shit of my boy to get him anywhere close to the top of the hill.
Seriously, though, this was a problem at one point.
Best as I could recall, we had 2 options back then: either use a thicker condom (or double up) or do you best to take your mind off sex (ie, imagining myself in the Dallas Cowboys locker room seemed to work ).
If that still didn't dull the stimulation, then you could pull out and stop until you calmed down, or squeeze the shaft to arrest the process (sometimes a hit miss prop).
Beyond that, I'd suggest you see your doctor. I've heard there are creams and pills you can take now that dull the sensation and sensitivity , but I've never tried those myself.
As to average duration of sex, I have no freaking idea. Stupid thing has a mind of it's own. Sometimes it's a few minutes and sometimes it can go for 30-45 minutes or longer.
Have just as much chance of predicting tomorrow's weather.