Variable rates

I have a student loan that is on an extended payment plan with a variable rate that is tied to prime. Currently, the rate is 2.11%. I have money available that I could put toward the loan, but at this interest rate, it seems advisable to invest the money. However, at some point down the road when the rates go back up, I may wish that I had paid off the loan early. Do you have any advice as to the best approach for paying off such a variable rate loan? Wendell, Rochester, NY