[IshKebab]

Someone else suggested that you have to replace your roofs every 25 years though. People definitely live for 25 years!!

Also even if you personally don't live that long, it does affect the value. For example a 99 year lease on a property is considerably less valuable than a 999 year lease, even though very few people live more than 99 years.

[AngryData]

25 years is common but most places allow 2 or 3 shingle overs that don't require a tearoff. They just slap a naked layer of new shingles over the old which is even cheaper than the first roof/layer.