Single ply roof guarantees usually cover 15-20 years, mainly focusing on...

https://wiki-aero.win/index.php/What_Would_Stop_a_Single_Ply_Roof_Reaching_35_Years%3F

Single ply roof guarantees usually cover 15-20 years, mainly focusing on material defects. But in reality, these roofs can last 25-40 years with proper care