Whatever the negative demands.
My main exposure times are usually between 10 and 40 seconds, and any burning required is in addition to that.
I draw a stick figure of the print where I note dodging and burning (at varying filter grades), note main exposure time, lens aperture, filtration, etc. This teaches me that it's important to be able to repeat the results down the road, and it helps me remain consistent with my work.
So, whatever the print seems to demand, I don't care what the actual number is, just that I know exactly what the number is.