Single ply roof guarantees typically cover 15-20 years, but these roofs 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 these roofs can often last 25-40 years with the right care. Guarantees mainly cover material faults, not wear and tear or maintenance issues