Oh blessed coco. Never let it completely dry. Once dry it's harder for coco to rewet unless you water reeeaaall slooow, otherwise the water likes to run through it. Let it dry some if you like but never dry. It's not good for the roots either. Depending on whether you are running pure coco or coco perlite mix can determine how often you feed/water. I feed everytime I water. Never plain water unless I am flushing. If unsure, practice lifting the pots to familiarize yourself with the weight to give you an idea of when to feed/water. Some say 10% runoff. Runoff is good. The key though to coco and runoff is that you are getting a good wetting of all of the medium. If the coco is dry lets say, and you water and see runoff, that does not mean you have good saturation. If your coco is dry you need to water slowly to get the saturation. What I did in the past was to give each plant a little watering then go to the next, making a rotation. I would do this until all the water was gone. This allowed a good even saturation. Lifting the pots helps learn/know when they are watered good. Then the runoff is legitimate.
Coco is a GREAT medium. I recently switched to coco chips on a drip system and am in love with everything about it. I can feed/push them harder and more frequently and they just grow like crazy. I say this in pretty much every coco thread I chime in on, but PH and calmag are your keys to success. If you don't PH to 5.7-5.9 everytime, or add calmag to every watering/feeding you can expect problems.
I can't see myself growing any other way other than possibly NFT as I want to do a vertical grow at some point. The only other reason I see myself growing in another medium is to try it, learn it, and master it. I would like to have all mediums under my belt in case I ever get the dream job of growing in a wholesale or dispensary grow op.