Single ply roof guarantees usually cover 15-20 years, but these membranes can...

https://www.slideserve.com/gwyneyxcez/why-do-roof-problems-show-up-after-two-winters

Single ply roof guarantees usually cover 15-20 years, but these membranes can last 25-40 years with proper care. The guarantee mainly covers materials, not wear and tear or maintenance issues