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

https://www.bokkmarking-signs.win/single-ply-roof-guarantees-typically-15-20-years-cover-defects-but-not-the

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years with proper care. The guarantee mainly protects against manufacturing faults, not wear and tear