Single ply roof guarantees typically cover 15-20 years, but the roof can...

https://www.slideserve.com/gwyneyxcez/why-do-roof-problems-show-up-after-two-winters

Single ply roof guarantees typically cover 15-20 years, but the roof can actually last 25-40 years with proper care. The guarantee focuses on materials and workmanship, not long-term wear and tear