I would assume you balance them fairly regularly, but in case you don't...

I ran a battery for about 10 charges w/out balancing and it seemed to suffer performance wise. After balancing it and charging again, I realized that it was probably out of balance and would not charge fully. It went from 800-1200 mah charge from before to 2600mah charge after balancing. It seemed to run short, but after balancing, it was strong again.