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

https://super-wiki.win/index.php/How_Long_Does_a_Single_Ply_Membrane_Roof_Last_in_Real_Life%3F

Single ply roof guarantees usually cover 15-20 years, but the actual service life can stretch much longer, often 25-40 years. The key difference is that guarantees focus on materials and workmanship, not ongoing upkeep