A single ply roof guarantee usually covers 15-20 years, but the roof itself can...

https://www.stall-bookmarks.win/single-ply-roof-guarantees-of-15-20-years-cover-material-and-workmanship-but

A single ply roof guarantee usually covers 15-20 years, but the roof itself can last 25-40 years if looked after properly. Guarantees often only cover manufacturing defects, not wear and tear or poor maintenance