With tobacco the physical addiction is broken in only a few weeks and depending on the individual that can be a hard or fairly easy time.
I quit cold turkey for 18 months because I just didn't feel like smoking anymore.
The real problem is the psychological addiction, if you can beat your brain you can quit if you can't or cannot motivate yourself sufficiently you are going to have trouble.
I can't recall the source but, I think I did read the average quitter will try 4-6 times before succeeding.
Living in Canada the one thing that seriously rattles my cage is "Health Canada" the joke that it is is stopping any e-Cigs/E-Cigars with nicotine from entering the country as best they can. Because, they are not big pharma products i.e. big money and they are not tobacco products so they aren't taxed stupid. And, of course the tobacco which is widely available is sooooo much safer.
The same clowns that did not stop nickel, lead and, cadmium laced kids drinking glasses from China from being sold here because, "they were meant for display not actual use".