What backpack are you using and what are you doing to it ?
Just don't go dropping it and it should be okay. Mine's about three-years-old and it gets a regular hammering and it's going fine.I've stuck it on a heavy duty trolley, since I was sick of breaking the smaller, flimsier, fold up types. It's a bit bulky, and definitely heavier; and the jury is still out whether I prefer the heavier sturdy sack truck, or the lighter, flimsy ones.
Put mine on a shopping trolley frame, the frame weighs less than a kilo so still easy to pick up and carry if I have to, but most of the time just wheel it around.