I went from 24 to 18 in the first month, and was hovering at 12 by the first vaping anniversary. Right now I'm bouncing between 3 and 9, depending on the tank/coil I'm using, and even the 9mg is strong enough that I take a few hits and don't touch it for hours at a time.
My fiance isn't willing to come down from the 12mg I have her at right now... but she's only been vaping almost 2 years. She "thinks" she's vaping 15mg, but that's only because I've not changed the labels on her bottles... Bwahahahahaha Personally, if she's happy with her 12mg, she can stay there as long as she wants
I don't think either of us will quit vaping anytime soon... we both enjoy the flavors and we both enjoy the little bit of nicotine...