Replace it now. An apprentice in my work bought a car from a garage (Clio '01 I think) and 14 days after warranty the cambelt went and his bill to rebuild the engine was £856.
That was almost 2 weeks ago and they still haven't completely fixed it, so he has to drive his sisters corsa with a pink steering wheel and pink seats whilst she is on holiday.
So the moral is...
If you need it replaced then pull your finger out and get it done, or face a hefty bill.