I quit caffeine before I started vaping because of trouble getting to sleep. I try to cut down my nic intake before I go to bed, but it just doesn't happen all the time. I usually use 24, but try to go to 6, 12, or 18 before bed. I also take melatonin and it helps a lot. I haven't had caffeine in about 6 months but sugar also makes my heart race too.