Info was gathered by the Kinsey report. There is an accessible statement of results on Wikipedia at
Human sexual response cycle - Wikipedia, the free encyclopedia
How long b4 u cum - the question of this thread is defined as from intromission to ejaculation and almost half of men report under 5 mins, with just 1/5th claiming over 10 mins. This is from self-reporting (so could reasonably be expected to be on the boastful side) - I've seen data somewhere from actually observed sex which gave significantly shorter times. Also of course it is age related - an 18 year old is going to be quicker. I think the figure is something like 90 seconds average at age 18, but I can't find it. And average means 50% are faster.
For all the guys on here who last much longer that's great, and we all know there are guys who can last. But I think it is important to point out that the average is much, much shorter than posts in a thread like this (or the average porno) suggests, and guys shouldn't get hung up about not lasting. Indeed extreme duration may be a result of nature or practice, but it can also be through the influence of alcohol, drugs, prescription medicines or illness.
The same Wiki page reports that while 80% of men cum in under 10 mins, only 6% of men believe they should cum in under 10 mins - about a third feeling that they should last until she orgasms. 76% of women believe a man should last until she orgasms or for 30+ minutes. There's a lot of male low self-esteem tied up in these figures - as well as unrealistic expectations by women.