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

https://lima-wiki.win/index.php/Do_Membrane_Roofs_Age_Better_Than_Older_Flat_Roof_Systems%3F

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years with the right care. Guarantees focus on specific materials and installations but don’t always include wear and tear or damage from weather