I know what I feel like after an analog or two but being that a cartomizer is the same as a pack it's hard for me to think of when to stop. Are you saying its going to take more time to get the nicotine buzz?
The answer is (1) you'll know and (2) no, a cartomizer is NOT equivalent to a pack. More like 4-5 cigarettes, I'd say. But I lost any equivalence along the way - there is nothing similar to the way I smoked in my vaping habits now. You cannot draw any equivalence in total mg of nicotine, or in vaping time. There is no meaningful relationship, but on the average, I'd dare say that no 1 PAD smoker is satisfied with 1 ml/day (that's what the regular carto holds). It's more like 4-5 ml/day, with a very wide range (I'd venture to say, from what I read on this forum, 3-15 ml/day).
I guess each may vape in their own way, and one's vaping routine may change over time. There's no rule.
I guess a lot of long time vapers tend to have long vaping sessions / chain vaping rather than brief "cigarette replacement" sessions.
I for one tend to vape long periods - 15 minutes to 1 hour; then I find myself going without a vape even for a full day. Very little in the way of actual cravings after a month or so of exclusive vaping.
In the beginning, I found it very useful to vape "preemptively" - start vaping when I anticipated that something was going to trigger the crave for a cigarette, like ending a meal or a TV show or n the morning or whatnot. I would vape as soon as I'd realize this might trigger a crave, and tried not to wait until I actually craved the cigarette.
It is very true what has been said - nicotine from vapor gets absorbed slower, so you need to give vaping a little more time: if, let's say, it took you 5 minutes to finish a cigarette, it doesn't mean that 5 minutes of vaping will suffice. It is, however, very individual, and it's hard to make generalizations.