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

https://redditchstandard.co.uk/lifestyle/how-long-does-a-single-ply-membrane-roof-really-last-a-building-owners-guide/

Single ply roof guarantees usually last 15-20 years, but the actual roof can often go on for 25-40 years with the right care. The guarantee covers materials and workmanship but not wear and tear or damage from neglect