What is the actual reason for having to replace a cambelt once it has been fitted to the engine? I did my timing belt and gear - new cambelt. 2 weeks later, all my oil seals needed replacing - new cambelt. Another 2 weeks and I suspect the increased pressure has blown my head gasket - another new cambelt?
In each case, I've only done about 1000 miles inbetween.
So, what's the reason? Is it to do with tensioning or just "would you risk it?"