Others may vary, but my experience dropping from 24mg/ml nic levels to 3mg/ml nic was pretty much a non-event. Over several months I just ordered the next nic strength down each time I ordered (once every three weeks). At no time did I have a nic fit. I just vaped a little more often right after the nic drop. I was pleasantly surprised that dropping vaping nic level was nothing like quitting smoking.
I've been at 3mg/ml for a couple or three years now and have no desire for more nic. Of course, like most my mod is either in my hand, in my pocket, or sitting next to me on the table at all times. It's a pacifier!