A single ply roof guarantee usually covers 15-20 years, but the actual roof can...

https://devinzort649.timeforchangecounselling.com/how-do-seams-fail-on-single-ply-roofs-over-time

A single ply roof guarantee usually covers 15-20 years, but the actual roof can last 25-40 years with the right care. Guarantees mainly cover materials and workmanship, not wear and tear or damage