Nico,
It's always, or sometimes, or never. You have to decide whether your testing qualifies as 'sometimes' or not.
Maybe if you sit down and watch TV vaping, and that session was on 0 nic testing a new flavor, and you do that once or twice a week, then it's 'sometimes'. But if you pick up a +nic cart straightaway after, and/or you only do that 0 nic flavor test every couple of weeks, you should probably put 'never', as it doesn't count for much.
We just wanted to try and get an idea of the rough percentage of people in each group. It seems likely that respondents are likely to be in any of the groups so the percentages might be reasonably accurate.
I don't do research or statistics of this type so there are likely to be many influences not factored in, though. For example one of those might be that people who use zero nic might soon cease vaping, as it seems more likely that such people would stop than those using say 12mg nic. And if they stop, they might well withdraw from ECF - so that the number of people using zero nic is therefore under-represented.
To me it's of interest to see these numbers and until somebody comes up with a real clinical trial result (which would be at least a 3-year study), these are the numbers we've got, and it's better than nothing.