As far as the regulation are concerned you can get a multiple entry visa valid for up to five years. You are still bound by the 90 days in any 180-day period maximum stay rule but if you don't exceed that, you can do as many trips as you want during those five years, paying the visa fee only once, with no extra paperwork.
The trouble is that you can't just ask for one and expect to get it. I don't think the rules explicitly say that anywhere but my understanding is that the five-year visa is mostly intended for UK residents (the UK is in the European Union and geographically very close to the Schengen area but not part of it).
As a US resident, you could probably hope for a two-year visa, which already gives you some flexibility. But you need to be a trusted traveller to get one (that is to have completed several trips on short single-entry visas) and to show you have a stable situation in your country of residence (thus being a student is probably less than ideal). It does not hurt to ask but consulates can always decide to issue a single-entry visa covering the trip at hand instead.
There is a bit of luck involved as well, I have heard about people getting a multiple-entry visa the first time around. The best you can do to help your case if you are not that lucky is to go several times through the bureaucratic process and respect the rules scrupulously. After several visits, you stand a better chance of getting such a multiple-entry visa.