Crumpler Australia is a manufacturer of quality bags and photographic backpacks. According to their website the company provides a lifetime warranty on zippers, buckles, fabrics, bindings, and workmanship on their bags.
My top of the range Karachi Outpost backpack has lost a tooth in the zipper. This backpack was only used on car and train trips and certainly has not been abused or had to rough it on any difficult trips.
The repair offered by Crumpler was to glue the zipper above the lost tooth. This may be satisfactory on some bags but certainly not on this model where the backpack has to be wide open to access lower storage due to narrowing opening.
I still think this is an excellent product by design and it is a pity their service does not match their own warranty statements. I have sent them an e-mail and I hope for a better outcome with this service issue.
May 24th update:
I have been called by Ben from Crumpler and I have been offered an alternative solution to my backpack broken zipper. This means I will have a backpack with a properly working zipper just in few days. Thanks Ben. This is how it should have been addressed in the first place.