Actually, the rubber bands can be re-used if you are carfull. I have a container with baby powder in it. After flying, I put the used bands in the container with baby powder and shake to coat the bands. The powder will help to dry the fuel and oil off the bands, thus allowing you to re-use them. However, you must check each band when using it to make sure it is in good shape.

I usually use 7-8 bands on each side when flying. If you re-used about half your bands, and used new bands for the rest, you should be in good shape.