I've used codeine to get off dope twice now. Both times I was taking anywhere from 300 to 500mg per dose initially, and tapered down to nothing. For me at least, tolerance does not build nearly as quickly as with other opioids, and withdrawal symptoms are comparatively VERY mild, I'm talking a walk in the park even compared to a mild OC habit (~40mg/day). For about two months I was taking high doses every day, and I never woke up in the night all fucked up or got anxious a few hours after dosing like I would when I was using harder stuff. I never ingested it more than twice a day, however, which probably made things easier on me. Codeine inhibits the enzyme that converts it to active opioids in the body, so you'll get a much greater effect by waiting 6-12 hours between doses.
Also, unless you're using pills without caffeine, you want to acquire ones with aspirin rather than acetomenophen or ibuprofen, as it's WAY easier to filter out along with the caffeine. Ibuprofen or tylenol-based pills require way more water to initially dissolve, meaning you've got a much higher likelihood of adulterants including caffeine in your final product. Using a supersaturated solution tek, my extractions yielded ~5ml of liquid containing almost all of the initial codeine, <50mg of caffeine and <50mg of aspirin. You just can't achieve those results with tylenol or ibuprofen.