OK, hear is one for ya. I changed the timming belt and didn't change the tentioner. It looked fine, so why change it. Well................... Months later I developed a rattle/knocking noise from the front of the engine which appeared to be the top center timming belt idler. After dissassembly; I found a tentioner stuck in full compressed position and a very loose timming belt. Thanks to the dumb luck gods; the belt never jumped a tooth. In addition to this I didn't change the water pump either and later had to take the front appart a third time.
The take away here is: The shortest, fastest and best way; is to do the job once and do it right! The trick is knowing right from wrong.
Show me a man that never makes a mistake and I will show you a man that never does anything!