How long should I set my timer for watering?

Hello everyone. I just got my setup going and I want to know how long should I set my timer to water? I'm going with Mr. Greens theory of watering three times a day. Here is some relative information that might help you better answer my question:

-Drip irrigation system (can be adjusted from 1 gallon per min. - 30 gallons per min.)
-Rock wool cubes
-Florescent lighting (2 cool, 2 warm bulbs)

I read somewhere that due to the density of the growing substrate (rock wool) you don't want to water it as much as other substrates. It retains water better and because of this over watering can impede the roots from receiving oxygen. With that being said, should I be watering them for a matter of minutes 3 times a day? Also, does the length of time you allow your pump to be on during water cycles change as the plant gets bigger? If so, please break it down for me. How much at 2 weeks from sprouting, 3 weeks from sprouting, etc, etc.

Wow. Is there no one out there who's got an answer to this? I mean there's gotta be a bunch of drip systems out there for the vegetative growth cycle. HOW LONG DO I SET MY TIMER TO WATER?

im using hydroton on drippers that are flood i run 15 mins every 2 hrs im just finished vegging and had no probs at all, Afghan kush special and black diesel.light cycle is 20 on 4 off, nute res temp is 20-21c

i go 3 a day at seedling stage at 15mins a go
4 times a day in veg at 15mins a go
5 times a day in flower at 15 mins
thats drip onto rockwool slab and it seems to work well
i also water at dark cycle so the rockwool is always damp

AH rockwool that would explain the gap between ur feeding holds alot of moisture i use root riots and they dont hold as much moisture so all is well in both camps that what we like to hear.

THANKS!!!!! I really appreciate it guys. I'm a noob to this so any information you guys can give me is crucial.