I’ve been addicted off and on since high school, and have quit a few times just to keep myself from getting too dependent.
Different people react differently. With some people, it takes a serious daily habit a long time to get them actually addicted. With some people all it takes is a soda a day for a coupla weeks. Some people have really bad withdrawal, some people don’t.
I always stop cold turkey when I quit, but I’ve learned to go to my doc first for some painkillers. The first time I quit, during high school, the withdrawal headaches made me so tense that I was getting tension headaches as well, and the two combined for the worst head pain I’d ever had (or ever would have, until I discovered migraines). Ended up on Fiorinal, which does have caffeine but less than I had been drinking.
Let me tell you, it’s no easy thing to go without caffeine for several months when you work at Starbucks and get the stuff for free.