My battered old Ortlieb panniers are still holding out, after more than 5 years of almost daily use. Someone at the coffee shop this morning asked me about them, and had similar luck with his own panniers.
This is something I love about the bicycle industry. There are so many good companies that really care about what they do. A lot of gear is built to perform, and built to last.
So many other industries produce crap that wears out fast, relying on planned obsolescence to keep their profits coming. Chalk this up as another sustainability benefit of bike commuting and bike travel. More greenbelt, less landfill.