Single ply roof guarantees typically last 15-20 years, but the actual roof can...

https://www.tool-bookmarks.win/single-ply-roofs-often-come-with-15-20-year-guarantees-but-their-actual

Single ply roof guarantees typically last 15-20 years, but the actual roof can often go 25-40 years with proper care. The guarantee covers materials and workmanship but not wear and tear or poor maintenance