Single ply roof guarantees usually cover 15-20 years, but the real service life...

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

Single ply roof guarantees usually cover 15-20 years, but the real service life can be 25-40 years with proper care. That guarantee mainly protects against manufacturing defects, not wear and tear or installation issues