The way you are watering is what a lot of beginners do, but trust me, it's not a good idea. The roots are not damaged nor do they die from the soil drying out. On the contrary, this is a very natural way for plants to grow; when there is no water available, the roots go in search of it. If you examine the roots of a plant watered properly and one that is kept moist all the time you will see that the one watered properly has a much healthier, and larger root system. I hesitate to say this but, this place is overflowing with bad advice; as a newcomer here I'm kind of shocked at the number of people who have no idea what they're talking about but giving out advice just the same. Now I don't want to come off as a know-it-all 'cause I certainly don't know it all; however, I've been growing since the 70's and have learned a few things along the way.
You're right about soil composition of course - makes a big difference. So does the size of pot you use. If you use one too big, it doesn't dry out fast enough and the roots are continually moist, which, again, is a bad thing.
For what it's worth, ProMix soilless mix is the best I've found for growing cannabis. Besides being a good 'soil,' you never have to worry about ph as long as you use this product. (It contains an agent to keep ph at a good level.)
So ... break free of that common beginner mistake. Let the soil dry out completely before watering. They'll thank you in the end.