It is not a concrete number. Some guys last several hours, other last less than 30 seconds.
Even with one same person I think it can depend on other factors, like the girl's vagina size, the beginning excitation, the last ejaculation to date, the room's temperature ??

But I think it depends the most on friction. The more in & out, the quicker you're gonna ejaculate. Be creative and don't do a straight-forward in & out in the same position. Make variations. (girls love that, and preferably no doggy, it seems to be the least wanted position for them)

but please do not use a chronometer to know when you're gonna ejaculate lol !

Ps: never forget: no sex without latex.

Actually, when my girl and I have sex, she loves doggy style. Getting a girl from behind is the best position to reach a girl's gspot. If you want to hear a girl moan...Get her from behind

We already tried ;-) doggy is not her fav. Sometimes we do it because I do like it. But she says she prefers me to be closer than that.

Different for everyone, there is no norm.