When should the camshaft be changed.

I was originally told at 60,000k's is when the camshaft should be changed on my 2005 Holden Astra.
I've just had the 30,000 service done and was told because of the age of the car the camshaft needs to be replaced. They said it's nothing to do with milage (As with a Toyota recommended camshaft change is at 100,000)
Am I being duped because I'm a woman or is this the truth. My car is booked in tomorrow to get the camshaft replaced you see.