My first Triumph Slant Bags lasted 4 years. They sat in the garage at night and outside during the day at work. I believe the last year required fiberglass at the bottom seams. I probably over loaded them (more than 6 lbs)? The rain probably didn't help. In any case, I bought two new sets for some strange reason. My second set looks good after two years and my back-up spare is in the attic.
