Well I think that PMP wants to be using it permanently as a cigarette replacement. While I don't think it's as dangerous because it doesn't contain all of the other harmful ingredients of cigarettes, and I'm pretty sure that you can't get lung cancer from it (which was always told to me as the greatest danger of cigarettes), I believe that Thorn said that it carries all of the same cardiovascular problems.
It would be better if he'd quit cold turkey or cut down on the amount of nicotine he's ingesting slowly until he's not using it anymore.