Dude here this has happened to me occasionally usually when I'm nervous and/or really turned on like say the first time I'm with a really hot girl. If this is happening to him ALL the time it might be some kind of mental thing.
Still I'm not sure why this is such a huge problem a reasonably healthy young man should be able to pop 3-5+ times in a session so if he goes off too soon just suck his dick or something for a minute and he should be hard and ready to go before long.