8 ml/day?? [gasp] If I went through that much juice each day I think I'd die - and I wouldn't have time to do anything else. {3 mg/ml times 8 ml per day is 24 mg of nicotine per day.} If you switch to 24 mg/ml you had better be prepared to cut your vaping back to one ml per day.
This kind of change is very difficult; it is very easy to over-puff and get nic-sick when abruptly raising your nic level by a large amount. However, it is really worth the effort. Take one or two puffs and wait! It takes about 30 seconds for the nicotine to reach your brain. If you take several more puffs before that happens, you will certainly regret it.
When I began, I was quitting smoking from 4 packs of unfiltered Pall Malls a day (plus a fair amount of snus). I quit with 36 mg/ml cartos and stick batteries. Chain-vaping, they would get so hot that I had to carry three at a time and cycle through them, letting two cool off while I vaped the third. I would usually kill 3 or 4 sets of three stick batteries a day. (I had 40 or 50 sticks and nine chargers.)
Once I began mixing my own e-juice (and using better mods and atomizers), I soon upped from 36 mg/ml to 50, and then after some experimentation to 65 mg/ml (which is my current strength). I now have cut back to a little over 1 ml of e-juice per day (around 100 mg of nicotine per day), and can go (as you hope to) for anything from 20 minutes to several hours between vaping sessions of two or three puffs. It's really nice to have both hands free most of the time.
