Single ply roof guarantees usually cover 15-20 years, but many roofs last 25-40...

https://www.ready-bookmarks.win/single-ply-roof-guarantees-usually-cover-15-20-years-but-the-actual-roof-can-1

Single ply roof guarantees usually cover 15-20 years, but many roofs last 25-40 years in practice. The difference comes down to things like weather, wear and tear, and maintenance