Single ply roofing guarantees typically span 15-20 years, covering material...

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

Single ply roofing guarantees typically span 15-20 years, covering material defects but not the entire roof’s life. In reality, with good care, these roofs can last 25-40 years