I have only been vaping for just over a month. Using about 18 mg I am averaging about three 5 ml tanks a day so 15 ml and I pick up the vape probably as often as I would have lit a cigarette which was not far under 40 a day. Although probably a lot of smokes but most burnt out by themselves in the ash tray. So I would guess 60 ml's in not to much and is probably due as much to boredom of a mechanical nature. People also say nicotine is addictive but I wanted to stop twice and stopped for two years each time cold turkey and I only thought the second week was the most difficult both times, not so much that I wanted a smoke as my hands craved the routine of taking out a smoke, lighting it and the whole action of busy hands. (I still reach for my top pocket every now and again.) I had the added advantage that although I drink, I don't drink and socialise much so I wasn't in the company of other smokers at a pub or restaurant.
It's a transition Stew, I can only encourage you to continue. People often ask me "Oh you are vaping, are you trying to stop smoking"
Then they look at my wife squiff as she bursts out laughing. She will then say "Oh I see you are crocheting, are you trying to give up knitting." or "I see you dyed your hair, are you trying to give up washing it."