Thanks for this thread RiddleMe, I use plant behavior as a means of telling what is going on. I say "behavior" because, if you watch your plants over time, after various stimuli, you will begin to see their behavior. Just like RiddleMe does when "Making it rain", watching the relaxed look when flushing, then watching water uptake, and then providing nutrients.
As an example, when I have early clones, after about a week, I take the cover off a while. Since my humidity is normally around 10-15%, they will begin to wilt quickly, and after restoring the humidity, they perk right up. As they progress, they wilt less and less as the cover is removed, indicating they are developing roots, and after a few days, they will not wilt much at all after a short time in low humidity, so then I know there are roots under that sand, so I can transplant, keep them in humidity cover a while longer, and then they are viable on their own.
One thing I have noticed to be true, is a perceived increase in potency on plants that were vegged to a nice old age before flowering, when compared to a small young plant flowered at an earlier age. I say "perceived" because that is very subjective. I have two AK clones now, one flowered at about 14", the other is still growing, and if not LST'd, would be about 3" tall now. Still vegging, and will give a comparison after it is all said and done.
Laters Yall!