Single ply roof guarantees of 15-20 years cover material and workmanship, but...

https://martinqigm171.bearsfanteamshop.com/how-disruptive-is-an-unplanned-re-roof-on-an-operating-building

Single ply roof guarantees of 15-20 years cover material and workmanship, but the actual service life can be 25-40 years with proper care. Factors like weather, maintenance, and installation quality all play a role