Using typical vermiculite substrate incubation, I've always found that I have to check moisture levels after the first month of incubation, and generally add more water. I haven't tried the press n seal yet, but even in the hovabator, they lose some moisture over time. Occasionally, I just set the eggs aside, and completely remix the vermiculite back to the right consistancy, then put them back.
I am hoping to try substrateless this year, we'll see how it goes.