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

https://www.4shared.com/office/Q9ZZDzKPge/pdf-27402-44163.html

Single ply roof guarantees usually cover 15-20 years but the actual service life can stretch to 25-40 years with proper care. The warranty protects against manufacturing faults, not wear and tear or poor maintenance