I used Rustoleum 2000 deg. high heat paint on my cyl. heads....507" Cadillac and the portion of the head is where the header bolts to is basically an extention of the exhaust port. The directions on the cans...both primer and top coat says nothing about a time frame as to when you have to heat cure the finish.....only that you do have to follow the 3 steps as outlined.
I must add that as skeptical as I was about these so-called high heat paint finishes this stuff REALLY worked and didn't even discolor during a long dyno session. I used Duplicolor 500 deg. ceramic engine enamel on the block and the can says nothing about heat curing. I wouldn't worry about your parts but do as 69 says and see what happens. Here's a pic of my cyl. head after the dyno pulls.......Dave