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

https://www.web-bookmarks.win/single-ply-roof-guarantees-usually-15-20-years-cover-workmanship-and-material

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years with proper care. Guarantees protect against defects, not wear and tear or poor maintenance