I have done 4000 miles from new and still get the very occasional clunky change going from 9 to 10.
I suspect it is when I rush the change, I never get it when I change gear slowly.
In the very early days I also got a couple of slips when the gears didn't mesh straight away. Changing the oil a couple of times certainly sorted that, so I would recommend an early oil change as a Christmas present for your hub. It may also help to change gear a fraction slower.