My yeti 170 tdi is 5yr old this month, has only done 38000 miles, I think the cam belt should be changed soon, what do others think bearing in mind the mileage

Mileage has nothing to do with it, it's done on age, 4 years for earlier cars and 5 years for later.

 

The belt goes stiff and starts to crack. It may go on for many more years but the change age is set on the safe side so virtually none fail before they are changed. There may still be one or two that go at an earlier age, but Skoda will have done a life to failure probability curve and decided where to set the change point to minimise warranty claims for belt failure, against too short a life putting people off buying the car.

 

We took a risk with my wifes low mileage fabia some years ago. It came to us at 4 years old and 40k miles with a just replaced belt and we did another 30k in the following 7 years before chickening out and changing it.

If you can afford it do it. If you can't, save up, beg or borrow until you can.

 

Its a bit like crossing the road without looking. Most of the time it won't be a problem...