I'm fine with some amount of exaggeration (and at least for me, too much realism can actually take me out of the story).
The guy comes twice, and you write about how this seldom happens to him, is caused by how hot the sex is, how he was longing to be with [partner] for a long time,... -- perfectly fine. If he comes 10 times in a row, you better have written multiple paragraphs of explanation for it (medical condition? experimental sex drug? not actually a human? [partner] has magical powers?) ;)