Well said space clam.... usually we put between 6 to 8 bands on trainer and some low wing 2nd planes.. micture of new and used.. discard any thing with nicks on it and go flying the wing hasn't move (or at leats moved enough to change atttitude) but on a couple of eagles the fuselage cracked from the repeated tension and 2 planes were lost... the rubber bands were ok upon salvage...
on the other hand they have saved the planes many times while training newbies