When to replace roofs?

[Casey S.]

I’m a pretty firm believer in performing repairs as soon as they are found in order to prevent more problems. Lately, as I drive around town I have been wondering if I am spending way too much money way too soon on replacing roofs. It seems like ½ the houses in this town are missing shingles and some of them are missing A LOT of shingles. These are almost all rentals and I have noticed many of them stay this way for many years at a time. These are middle class type properties so I assume they aren’t leaking or someone would be pitching a fit and they would be fixed. On the other end of things, if you ask an insurance company or inspector, they seem to think any roof more than 6-7 years old is at risk for catastrophic failure and likely to blow off in one big piece at any second. How do you seasoned pros decide when to drop the cash on new roofs?