I just read a article where it said you should inspect your timing belt every 10,000 miles. Obviously the fellow who wrote this has never inspected a timing belt. The majority are difficult at best to inspect. True a few models have an easy to remove upper cover but this is the exception. I would suggest inspecting the belt every 25,000 miles after the original replacement. Then replace it at 100,000 no matter how good it looks.When inspecting look for hairline cracks along the face of the belt, a few are OK but any more replacement is in order, also check the drive side of the belt for missing teeth, if any are missing, replace before starting the engine you have already lived on bored time. Also check for cracks on the drive side. If the belt feels brittle, hard to twist, or has a dull color or is very shiny replace also. Usually one quick glance you can tell a belt that is due replacement. They just look defective. One more thing to check if for any anti freeze on or around the belt. Belt replacement on some vehicles can be very expensive but it is worse to put it off and have it break, it can cause serious valve train damage which on some vehicles can exceed the worth of the vehicle very easily.I only have one vehicle that has a belt and that is my convertible which I seldom drive and I will replace that belt every 3 or 4 years and I don’t inspect I just replace it. But it is an easy one to replace. Timing belts work great, they are quiet, easy to flex so they can drive several cams plus in some situations the water pump. But they do require replacement