I did mine at 20000,Im sure it doesnt make a difference,but others will chime in..

 

Just use the FSM torque order... there are a couple of the OE washers that seem to be a pita at first, as they are slightly under the edges of the valve springs. Here is where a magnet/long needle nose pliers is/are very handy... makes the job a cinch.

If you do have higher mileage... or have altered the "tune" of the car, I would be inclined to first run a compression check to make sure everything is in good order prior to the "one at a time method".