Single ply roof guarantees typically cover 15-20 years, but the 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 typically cover 15-20 years, but the roof can actually last 25-40 years with proper care. The guarantee focuses on materials and workmanship, not long-term wear and tear