Hi, I would agree with some of what your mechanic says, he is quite right that the belt should be changed on time period as well as kilometres travelled. In the UK the timing belts change is due at 72000 miles, approx 120,000 kilometres. OR six years, personally I think this is too long, I would rather change the belt every 36,000 miles or 3years, this way the belt will be used for only half its design life and so should be able to cope better with unforseen stresses.
I don't think you need to change the cam timing variator, pulleys etc, but I do think the tensioner bearing would be a good idea, (if these fail they cause alot of damage).
I hope this is of some use to you, at the end of the day though you have to trust the person doing the work for you.