https://texaspatiobuilder.com/replace-your-roof/
In general, metal roofs should be replaced every 40-50 years to ensure that they continue to provide adequate protection for your home. Tile Roofs: 50-100 years.

https://www.reddit.com/r/Home/comments/15i1a6k/when_to_replace_a_roof/
A typical asphalt shingle roof will last about 20 year, with variations depending on a lot of factors. As an example, I just had my 25-year old ...

https://www.kin.com/blog/when-to-replace-your-roof/
The age of your roof is a good starting point to determine when it's due for a replacement. Experts usually say a roof should last about 20 years.