I don't think that you dropped to fast... It depends on your devices as well.
I dropped within 4 months from 18mg to 6mg and now I am vaping under 3mg (homemade).
The amount of nicotine which you get from your mod differs if you, i.e.
use of a rebuildable device or even a dripper (I don't want to get to specific here

)
inhale mouth to lungs or directly to lungs (even with non rebuildable devices)
If you do not change the device and you feel like you have the urge to get more nic...use 12mg again and just wait some time to adapt again and soon enough I noticed that you just want to decraese the amount of nicotine and eventually do so
I hope this gives you an idea of how you can "play around" with the amount if you want to
Happy vaping !
And a big thumbs up for quitting after such a long time !