Mister Timing?

I have been reading A LOT about aero and have started a grow. This is actually my third aero grow, but the first had to be saved with a NFT dripper, and the second didn't get enough mist. Now I seem to have the other problem. My clones are still alive, but not much new roots and the medium (Rapid Rooters) seems wet. I am running a mid pressure system at 40-60 psi with misters that do 0.6 gph of 55 micron drops and have a timer that will go as low as one sec, with on times that can be less or as long as I want. Currently I am on 10 sec, to get all my misters running full pressure for at least 5 sec (to much pipe--fix it on the next grow) and off for 10 minutes. Should I extend the off time? How do I know the best timing?
Thanks