Single ply roof guarantees usually cover 15-20 years but the actual service...

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 actual service life can stretch to 25-40 years with proper care. The warranty protects against manufacturing faults, not wear and tear or poor maintenance