Wagwan...
I would watch out about watering as rigidly to schedule as some guides tell you to because not only is the soils drainage somewhat important, the most important aspect is how your plant deals with the water u give it. The way plants deal with water is dependent on the age and atmospheric variables (light power/type, air: circulation and exchange, humidity and temperature) that exist in your grow space. All of these variables influence the tranpiration of any living plant. Strength of fertilizer in solution, if too concentrated, also alters how much water a plant uses by disrupting the way water distributes itself from grow medium to the roots and plant.
Im not trying to complicate things but to suggest to you to follow advice about watering only as a general guide and to observe as best as you can allow how your grow room and horticultural practices combine to change a plants water usage. I've learned this through actual experience by thinking if i added lots of perlite that the extra drainage would solve my problems with promix taking 1 WEEK+ to dry when the real problem seemed to be my fuck up or due to bad room syndrome.
I don't have enough experience to say this, but what I seem to understand from what i've read is that you must keep your roots as healthy as you want to keep the green healthy. A lot of shit actually happens in the rootzone that i thought weren't so important.
Later.