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

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

Single ply roof guarantees usually cover 15-20 years, but the real service life often stretches beyond that, up to 25-40 years. The guarantee focuses mainly on material defects, not wear and tear from weather or use