Wear and tear warranty woes

I recently had my 2010 Toyota Hilux SR5 diesel in for the 40,000 km service and was asked to bring it in the night before, as they needed to check valve clearances while cold. The following morning I got a call telling me the shims and buckets needed re-shimming/ replacing. I was then told that this was a wear-and-tear item and wouldn't be covered by their fixed price servicing or warranty. They have quoted two to three days to do the work at a cost of approx. $800. I can't believe an internal part on a diesel engine could be considered a wear item and especially after 40,000 km. Do you think it is reasonable that it's not covered under the warranty or standard servicing?

Checking and adjusting the valve clearances is a part of the service schedule on the Toyota diesel, and the parts do wear out. This is a case of buyer beware, you really need to check the fine print on the warranty to find out what isn't covered before you actually spend your money.