Generally speaking, itís wise to get your roof inspected when it gets to be about 10 years old. While most residential licensed roofers are going to install a roof warranted for at least 30 years, not all roofs are installed by professionals, and their workmanship or materials may be substandard. It is also very possible that although your roof hasn't yet reached its life expectancy, there may be reasons for repair, such as damage that occurs due to severe weather. Flashings, roof valleys and chimneys in particular are subject to leaks. In addition, some homes, due to inadequate roofing insulation, are subject to ice jams (or ice dams), which is when the heat rising from the house melts some of the snow so that the resulting water flows to the overhang or gutter (where there is no heat) and then refreezes, causing larger-than-normal deposits of ice, which, when they melt, can cause leaks. Keep in mind, too, that stains, blisters or flaking paint on interior ceilings or walls can be indications of moisture build-up and should be thoroughly investigated. The way to know for sure is to get a roof inspection.