I use Ortlieb Classic on my expedition tour bike and Lone Peak on my Giant Excursion road tour bike. I have full sets, front/rear panniers, handlebar bag and rack bags. I don't necessarily use all bags on all tours. I like the flexibility the systems offer. Good advice on not packing the bags full at the outset.
I don't have a problem self limiting the amount of stuff I pack. I occasionally go out with a bag empty, but it is usually because I am planning on picking something up along the way. Make a packing list and stick to it, also review the list before/after every trip and remove non essentials that don't get used.
Aaron