I presume you are referring to the cam belt or timing belt as it's otherwise known. If so then I'm not absolutely sure but I would think it would be around the 96.000 miles mark which is what the Ford Focus and the Volvo V50 are which the Volvo is built on the same chassis.
The cam belt must changed at 125.000 miles or 10 years plus there is also a chain or drive belt running in oil from the crankshaft to the fuel pump which must be changed at the same time making this a very expensive maintenance repair.
I wonder if it has ever been tested in court....Suppose a car is serviced its whole life by main dealer & belt or tensioner fails before manufacturer interval? Tbf cambelt related failure on modern cars is almost unheard of.