I know for a fact that there are some vehicles that can end up with a ruined motor if the belt breaks. From reading on the site that WI linked to, it sounds like your car could be one of them. (The cars I have known this to happen on were 4 cyl. Fords) Bent valves and holes in the pistons... it was ugly AND expensive. I'd err to the side of caution. I'd also add that your driving habits could influence your decision as well. Do you drive your car hard, launching at stop lights and such that could put more stress on the engine/belt or do you drive fairly benign, casually bringing your car up to the speed limit and not exceeding it? If it's the former, don't wait to long before changing the belt. If it's the latter you can likely wait until the 100k mile mark.

Has the service dept given any reason for changing the belt now, rather than when the manual states to do it?

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