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

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 real service life can stretch to 25-40 years if properly maintained. Guarantees mostly protect against material failures, not wear and tear or damage from poor upkeep