When the ol' 120K timing belt changeover comes up, in addition to having the seals at the front of the engine and the water pump & hoses replaced, I would seriously recommend you go ahead and spring for a new harmonic balancer/crankshaft pully as well!
SERIOUSLY!
Mine self-destructed last Friday. The timing belt cover had a hole worn through about 270 degrees of rotation. The belts were gone, gone, gone... I'm fortunate in the fact that there was no damage to the brand new timing belt, seals, etc.
If you do a search using "harmonic" on this Forum there is a beautiful picture of somebody's cover and a new one: mine looked identical to that pictiure, and it is not a pretty picture.
I've been really lucky these past dozen years: other than the damned/endemic REAR WHEEL BEARINGS this is the 1st and only MECHANICAL failure I have ever experienced outside of the original factory 5 year/60K warranty. To my knowledge the pully has only been off the car twice, at 60K and just recently @ 120K. I don't think I would now really trust one that has been on & off many times using a strap wrench, etc.
I keep my belts properly adjusted. It just detonates at some time, probably based upon mileage, heat cycles, age... If you notice a wobble or any indication that it is beginning to separate
REPLACE IT ASAP!
It has made a believer out of me. I know the balancer/pully is a little on the expen$ive side, but THIS is not an experience you want to be subjected to and can be easily avoided. I doubt if I'll ever need to buy another one, but who knows?
When I hit 240K I'll be more than happy to buy another replacement! With any luck I'll still have an intact one to use as a spare.
Cheers!