I have been on wellbutrin over a year. I've been on prozac and some others as well but I generally build up a tolerance after a few months. I thought I had built up an immunity to wellbutrin as well and started taking it less then quit taking it just to see if it made a difference (i'm ttc) and I felt horrible. I had no desire to get out of bed, so it does help me alot. I am not looking fwd to when I get pregnant and i have to eliminate it.
I have noticed that when I don't take it for a few days then I take it, it does give me a ton of energy and makes it hard to sleep. but after a week or so I am back to 'normal'
Overall it is one of the safer depression meds if you need to be on a prescription med. I had a psychiatrist prescribe it to me at first but I don't see her anymore and my family doc has no issues continuing my prescription.