Cam belt intervals on WRX

[S6 ROR]

Not really being up on the marque, could someone pease advise at what intervals the Cam belt should be changed on a 2.0 WRX.
Is it done on mileage, or would you also suggest being changed on age as well.
Looking at a car tomorrow on a 53 plate which has done 77k with full history. So, at 10 years old, when will next change be due.
Ay advice will be much appreciated.

[Goldmember1]

All the WRXs are 5yr/50,000 mile cambelt change, so it'll be due to be changed this year .. would recommend doing it on age rather than mileage.
HTH .. Good luck!