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

https://www.tool-bookmarks.win/single-ply-roofs-often-come-with-15-20-year-guarantees-but-their-actual

Single ply roof guarantees usually run 15-20 years, but the actual roof can last 25-40 years with proper care. Guarantees cover manufacturing faults, not wear and tear