I bought a 2006 MDX with 99k on it. How important is it to change the timing belt

Since that model has an interference setup you could potentially bend a valve or destroy a piston if it snaps while the engine is running. Autozone says it should be replaced every 105,000 miles or every 84 months under normal operating temperatures. It's also a good idea to replace the water pump when changing the belt.

y Uncle's dealership went to 95000 recommended change as they saw a number of failures before the recom 105. Since the water pump is off its simple to mount a new on and new belt, cheap insurance against failures.