Single ply roof guarantees usually last 15-20 years, focusing on the product...

https://wiki-net.win/index.php/What_Does_%27Component_Selection%27_Mean_on_a_Single_Ply_Roof_System%3F

Single ply roof guarantees usually last 15-20 years, focusing on the product and installation quality at that time. However, the actual service life can stretch to 25-40 years with proper care