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

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 roof itself can last 25-40 years with proper care. The guarantee mainly covers material faults, not wear and tear or issues like ponding water