Have no "rules" for vaping. Through trial and error, I found that I am quite satisfied with about 6-10 mg juice in the morning and puff on the ecig from time to time. one puff, put a few dishes away, an other puff, wake up the kids, an other puff...etc. At work, where my vaping is not as frequent, I need some 18 mg with lots of puffing before going back to a couple of hours away from my ecig. In the evening, I tend to puff at regular intervals and will be at 18 mg or higher.
Here is the kicker: I have monitored my juice consumption / nic concentration and am hovering at about the same nicotine level I was consuming daily as a smoker.
The only odd thing I have noticed is that a given flavor will be perfectly satisfying for a few days, then it will do nothing for me, and I need to switch to another flavor to get the same level of satisfaction. After a few days, the same phenomenon occurs, and I need to change again (or get back to the previous flavor).