Timing belt alignment is one of the major factors affecting timing belt life. If your timing belt is misaligned, it will most likely be rubbing against something that it shouldn’t be rubbing against. This will increase the amount of heat your timing belt must deal with, which will cause the timing belt to weaken and fail much sooner than it should. Signs that your timing belt is misaligned are very hard for the untrained person to notice. With the engine running, you will hear a rubbing or scraping sound emanating from under the timing belt cover. You may also hear a whistling or whining type sound.
For more info, see Signs It’s Time to Change a Timing Belt