Leaving Germany but keeping the bank account open

Next week I will return to the U.S., but I must decide whether to keep my bank account open. I don't know when I will return to Germany, hopefully about 6 months to a year from now. I'm just looking for some advice on if I should keep money in the account or if I should transfer it now. It's a student account and I get no interest, but with the Euro doing well, I think it's good to have some money available overseas. My visa is valid until March - does this matter? Also, are there any tax regulations about keeping money here while not living here? I don't think there will be any problems, but has anybody done this?

Tax is only applicable if you make capital gains. No gains no tax. This at least from the German viewpoint.
Whether the bank will claim that you are no longer a student and start levying bank charges is another matter.

Keep it, especially as it's a student account (i.e. free, presumably).