I took effexor steadily for about 6 months. It took 1 month to quit, and finally the doctor said to just stop, so I dealt with serious withdrawl symptoms for about a week and I was clean. The best way to describe the withdrawl was what I would immagine a small seizure to feel like, just electric shocks in my head and throughout my body. I had worked myself up to a pretty high dose though. I just got sick of days when I would forget to take it and have to deal with the withdrawls.
It was weird because I'd never had symptoms like that before. I took 5-6 percocet a day for about 4 months and just stopped no prob.