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

https://claytoncllo171.tearosediner.net/approved-contractor-schemes-do-they-actually-matter-for-guarantees

Single ply roof guarantees usually cover 15-20 years, but the actual service life often stretches to 25-40 years. Guarantees focus on materials and workmanship, not wear and tear or maintenance