Single ply roof guarantees, usually 15-20 years, cover specific materials and...

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

Single ply roof guarantees, usually 15-20 years, cover specific materials and workmanship but don’t always reflect the full service life, which can stretch to 25-40 years with proper care