2008 YZ450F Valve replacement questions

Hello all,

Hoping to get some advice about replacing the valves in my 2008 YZ450F.

I've owned the bike for 2 years and would estimate that i've put 60-70 hours on it, but i've got no idea hour many hours on the internal prior to buying it (seller didn't advertise it as recently rebuilt). I've always replaced oil & filter after each 3 rides (7.5hrs-ish) and checked and adjusted valve clearance a roughly 20 hour intervals. 4 rides (10 hours) back I replaced the piston, rings and timing chain and checked the bottom end bearing, so valves are the one big thing left to do.

After I did the piston replacement my inlet valves were all at 0.10 (one was a bit tight though) and both exhausts at 0.20 (specs are 0.10-0.15 for inlet and 0.20-0.25 for exhaust)

I'm re-checking the valve clearances again and after 10 hours the inlets are 0.08 on the one that was tight and 0.09 for the other 2 and the exhausts still at 0.20 (admittedly my feeler gauges only have a 0.20 and then a 0.23, so the exhausts could be 0.22).

Would tightening over this time period be an indication that I should replace the valves, or at least pull the head back off and get it checked over? I'm trying to keep costs down (I know I know, got to pay to play) but its cheaper for me to import a valve kit from USA than buy them locally! and that's not including work to the head itself.

Also if anyone is from Sydney, Australia id appreciate any recommendations on who to take the head work to, if required.

Thanks in advance.

DC