I had tried to quit a few times over the summer, never got past 4 or 5 days. I got a knock-off 510 to start with, and it was ok at first, and I immediately cut how much I was smoking in half.
I got tired of cartridges pretty quick, and moved to cartos. That upped the satisfaction I got from vaping, and I again started smoking less. At that point I would have a cig once or twice a day, mainly for the "ritual" of going out to smoke... sort-of getting away from things for a few minutes and enjoying a habit I had enjoyed for ~15 years.
One day I ran out of smokes, and didn't feel like going to the store. But then the next day I still didn't feel like going, and the next day, and the next, and then I just didn't care. Now I've got an eGo-T and I've had maybe 2 or 3 in the last month, bummed from my neighbor because we were standing outside chatting and I didn't have my eGo with me and he offered.
I honestly put no pressure on myself to quit, because of how crazy I had felt when trying to quit cold turkey. I just figured if it happens, it happens. And it happened.