When my brother "borrowed" my LegendII (didn't ask, he just took it), he did just that, filled the bag until it was so hard the bag would stand up on it's own, and he split the filltube, so it was in a right mess, and he said "it's not picking up any more, it's broken", and I was "It's not broken, it's just in the hands of an idiot who doesn't bother to change the damned bag!!!", of course, he now does not have said LegendII, that's in pieces out in the workshop cos it has so many deep gouges in the metal that were not there before, needs more work than I can be bothered to do, still runs fine though, just looks beaten up...
My advice, do not lend anything out without asking for a monetary deposit first, any damage and you keep the money to pay for repairs and replacement parts...