Remicade put me in remission but I stopped it after a year due to allergic reactions and loss of response. Mastersmom, my GI says we may need to try it again, my rheumy doesn't think it's a good idea since I had bad reactions. Most of what I find online says NOT to restart it, so I'm saving that as a last resort (which I am getting close to being at).
Next, I did Cimzia on a clinical trial, so I was getting the full dose every 2 weeks instead of the 4 weeks that is now FDA approved. I was on it for a year and it kept my Crohn's in remission but didn't completely get rid of the arthritis, so I switched to Humira when the clinical trial was up. Humira didn't help much with the arthritis, so I switched back to Cimzia after about a year. Now I've switched back to Humira again after about a year because I have less stomach pain on Humira than on Cimzia and neither are taking care of the arthritis. Neither meds are working the whole 2 or 4 weeks for me and my docs say they can't get them approved more often.
So, a year seems to be the average length for me.