If you are not sure of the "routine" maintenance that has been done to a car because you are not know its complete history. Do it all yourself or have it done it after you first get the car.

This ensures that it HAS definitely been done and you'll know when as well.

If it's 135K and you're the slightest bit unsure or doubtful of that dealership, have the timing belt done. If it were the original one and it happened to break... You're screwed.