Personally I've never had an issue with the zippers. I think the issue comes when you stuff the thing so full that it weighs about 90 lbs and is bulging at the seams... I can put 5-7 days worth of clothes, sneakers and a medium size shaving/toiletries kit in mine without any problems. If you get one of the snap on bags that clips to the front you can take even more along (I attach my laptop).

I bought my PNT through http://www.luggageworksonline.com. They offer reduced rates for crewmembers if you can provide some company/crewmember information.