If we are to believe science, there ain't nothing wrong with a little semen exposure. Actually there ain't nothing wrong with a whole lot of semen exposure
But here's one of the finer points on the matter, though, before you go out and do something we wouldn't: The benefits of prolonged semen exposure are experienced pretty much only by pregnant women.
Researchers in New Zealand have discovered that long-term repeated exposure to the same person's semen helps raise a woman's tolerance of the paternal antigens found therein. This kind of "semen immunity" in turn leads to a decrease in preeclampsia
(pregnancy-induced hypertension -- no fun) and also reduces the likelihood of delivering an undersized baby.
So, it's more about having a long-term, exclusive sexual relationship than anything horribly kinky. Unfortunately.