I was given a Trek Pro bicycle saddle bag as a gift about a year ago. This past weekend, the zipper on the bag broke. I emailed Trek customer support and was told that the warranty expires after a year and that I was out of luck!
Trek's bicycle warranties are great, but I'd recommend against buying any of their accessories due to this very poor warranty policy. Other companies (like SunLite Cycling Gear) have lifetime warranty on all of their products. Either that, or buy the Trek stuff at REI so you can return it when it breaks :)