I'm not old enough to have smoked for 25 years, but I smoked for a couple of years (I don't disclose how long in order to protect myself from PBJ), and when I quit, it was cold turkey. The first week was alright. The second week sucked. The third week was better. I was really irritated all the time, but after the second week, it got better. Still irritated all the time, but it's not because of nicotine withdrawal anymore :p. Also, food tastes way better after 72 hours of not smoking. Someone told me that, and I thought it was crap, but it's true. Good luck man. May the force be with you on your journey.