It depends also on the age - the younger you are, the more probability there is that premature ejaculation can occur and the more probable it is that when you are older and have regular sex (and if possible as frequent as you need) it will improve a lot.
Meanwhile, I think that Exodus5656 (previous poster) is right, you can masturbate or have sex (oral or intercourse) as often as you need (or as often as possible).
Another suggestion may be - you can try using condoms (some of them desensitize penis a little bit) or some creams or gels which make penis less sensitive (I have no experience with this, so I do not know for sure if it helps).
Moreover, after the first ejaculation (if it happens quickly), you can please your partner orally or manually, have some sexual plays with her and after some time you may have erection again and then you can last a little bit longer, too.
But above all, I would give up some unrealistic expectations (4-8 hours), of course if you have more ejaculations in one session, then the sex can be longer, but to last 4-8 hours before having the first ejaculation of the day seems to be unrealistic and absolutely unnecessary (probably even not very healthy). Don´t forget that even porn movies do not last for 8 hours per one ejaculation and by the way the performance of porn actors is unrealistic too, far from reality, not very suitable role models for real life ambitions...
Good luck!
severin76
I would say masturbate more it helps desensitize the penis and the many nerves it has.