Peel the bananas, separate them into single-batch packets - leftover plastic bags, tupperware, old cottage cheese containers, etc - then freeze them like that. When it comes to making bananabread, they don't have to resemble bananas. Voila! Non-perishable.

Also, if you have limited numbers of tupperware, you can mash & freeze the bananas, then once frozen pop them out of their "molds" & put them in a big old bread bag for freezer storage.