Single ply roof guarantees usually cover 15-20 years, but the roof can often...

https://www.acid-bookmarks.win/single-ply-roof-guarantees-usually-cover-15-20-years-but-the-actual-roof-can-2

Single ply roof guarantees usually cover 15-20 years, but the roof can often last 25-40 years if looked after properly. The guarantee mainly protects against manufacturing faults, not wear and tear or poor maintenance