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

https://www.bookmark-belt.win/single-ply-roof-guarantees-usually-cover-15-20-years-but-the-actual-roofing

Single ply roof guarantees usually cover 15-20 years, but the roof itself can last 25-40 years if looked after properly. The guarantee mainly covers material faults, not wear or damage over time