This seems to happen with some frequency using non protonated nic. It not infrequently takes years. I used to vape 24mg in MTL. Now I’m vaping I think 10. I jumped up to 24mg again during Christmas for a long road trip to minimize the amount of vape fumes in the car because the other trip memeber suffered from severe breathing problems. When I got back I was at 10mg DL, but I’m now finding a few months later that I’m preferring the 10mg in MTL. I need to cut my 10mg in half and try that in DL I think.