I've also been noticing that my body doesn't handle my current 12mg level all that well anymore, either. I started at 24, and tried to drop after the 1st month to 12, but that set me back to smoking a couple now and then. After 2-3 months of other issues I had to deal with, I started vaping exclusively again and using 18mg. I think that was in Sept.
In November I dropped down to 12mg, and since December when I got my iTaste VV I'm noticing that my 12mg is making me very jittery (no head rushes or headaches, just a jittery and unsettled feeling). I think my next juice purchases will be 6mg, and I'll mix that with my remaining 12mg.
Some of the health issues I've been dealing with over the last 6 months have really thrown me for a loop, and I'm not supposed to have ANY stimulants at all. Doc understands that if I need it to function I can have a cup of coffee, but NO caffeine after 1pm. I think the nic is also affecting me so dropping down can only be good. As it stands, I can barely handle 8 oz of coffee anymore, and my 2-3 cans of Diet Cokes a day habit has dropped down to 1.
I never had a goal to drop my nic, but it seems that my body is telling me that I want to and should.