I see black market as a viable option for all vapers (regardless of age) who are serious about their desire to vape.
That it is illegal will not be a deterrent for most. It is illegal to drive over the speed limit. If you get caught driving over the speed limit, you lose points off your driving record and pay a hefty fine. I think in all my years of living, I've met 5 people who only drive the speed limit. I could go on any highway right now in the U.S. and rather easily establish that 95% of the drivers do not seem to mind, even a little bit, that they are engaged in something that is not legal.
if eCigs have "saved your life" and there is strong desire to continue to use them, you'll find a way to get exactly what you want. Perhaps not anytime you want, but then again, perhaps anytime you want.
Plus, very existence of a black market, serves as a wide scope by which to protest heavy handed regulations.
We have historical awareness and current examples of items that were once prohibited are now legally marketed (and regulated) because legal jurisdictions learned, over time, that making it illegal did not serve the public good.