Single ply roof guarantees usually cover 15-20 years, but these roofs often...

https://wiki-fusion.win/index.php/What_Does_a_Manufacturer_Design_Service_Usually_Include_for_Single_Ply%3F

Single ply roof guarantees usually cover 15-20 years, but these roofs often last 25-40 years in practice. That’s because the guarantee focuses on materials and workmanship, not wear and tear or accidental damage