The F-stop warranty is pretty clear about wear and tear (see below). So what is "extended use" relative to the warranty period. I have a LowePro bag about 3 years old and I suspect except for the tags missing it could be sold as new since it totally lacks abrasion on the bottom. I also have a SwissGear computer bag, close to 10 years old and used 5 days a week but it barely shows abrasion.
What Does This Warranty Not Cover?
This warranty does not cover rips, burns, tears and damage caused by improper care, mishandling, misuse, alteration, or accidental damage; nor does it cover the natural breakdown of materials that occurs after extended use (i.e. zipper wear, fabric abrasion, etc.).
Also, this warranty excludes all claims to any incidental or consequential loss to personal property. Some states, provinces and countries do not allow the exclusion or limitation of incidental or consequential damages, so this exclusion may not apply to you.