Quite a few name-brand packs offer lifetime guarantees. I used to work at a camping store, and all the brands we offered had such a guarantee. I used to have to send packs back. The company gets to choose whether to repair or replace the pack; usually they'd replace. The guarantee is only on the seams and zippers -- the only items that really wear out.
Personally, I'm a fan of LL Bean products, but Lands' End, Jansport, NorthFace, and other brands are really all in the same ballpark.