The service schedule is there for a reason.
You will note that it is both mileage & time dependant.
That is because some items degrade with a lack of use as well as a lot of use.
If you had seen the state of a set of belts that had only done 2000 miles in 2 years, you would have been happy to pay for the service which found them rather than wait until it had 6000 miles on it ( not that they would have lasted that long. )