I read that with nicotine, the actual dependency is over in 48 hours.
I don't think so. In terms of addicitivity (if that is such a word) nicoteine ranks right up there with heroin. That is why it is so hard to stop smoking cigarettes.
Cannabis, on the other hand, can have, merely, a psychological potential dependence. Although some level of tolerance can build up, it is nothing compared to alcohol, ciggies, coke, caffeine, or other substances.
I started smoking grass when I was 12 years old. I smoked heavily for about 10 years and then quit abruptly with no effects whatsoever. I didn't take any drugs at all and I drank very little booze for the next 16 to 18 years. (I got very heavily into weightlifting and boxing and I lost all interest in getting high.)
Then a few years back, I decided to once again partake in the ganja. I got high, but I did NOT think that I got particulaly high given my long abstinance from cannabis.
While I no longer have the desire to go out with my buddies and drink and toke till I am completely mashed, I think that has more to do with the fact that it gets old real quick and, as an adult, I now have real responsibilities.