I really don't get your first point about only being a student once. People go to bars and meet people all the time and the women I know with the highest count of partners met them outside of or after uni. The "only one chance to do this" doesn't really make any sense. If anything it's worse when it's guys from your uni as they often share social circles and your chances of a reputation are much much higher.
The risks you're taking are the same as anyone having casual sex anywhere, which I assume you're aware of. For women it's the risk of not being able to change your mind - if he gets creepy on you and you don't want to sleep with him after all, the chances of rape are higher when you're alone and you already got him hot and bothered.
Then of course there is the risk of reputation, which as long as you are protected, is probably the largest one. That risk is present whether you agree with the term "slut" or not. How men react to a girl who's slept around varies from guy to guy, culture to culture and his own sexual life. But most of the high quality men I know who have good options with women would not want to end up with a woman who's known for having "been around", whether they admit to it openly or not. They're not conservative guys either - they're raised in liberal, feminist countries but like the idea of being committed to a woman who is selective with her sexual partners. It's the kind of thing you don't become aware of until you are, at which point you can't really do anything about it. It's all up to you really. Some girls still find it worth it.