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

https://xeon-wiki.win/index.php/Managed_Decline:_Can_You_Plan_Replacement_Without_an_Emergency%3F

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