Remicade should be considered a long term drug. You will very likely stay on it for as long as you experience good control of your disease, without any issues with the Remicade itself. I'm not sure if there's and statistics that show percentages of users and years of use, but I have heard of many Remicade users being on it for 10+ years.
My daughter was diagnosed Feb. 19/07, (13 yrs. old at time of diagnosis), with Crohn's of the Terminal Illium. Has used Prednisone and Pentasa. Started Imuran (02/09), had an abdominal abscess (12/08). 2cm of Stricture.
Started Remicade in Feb. 2014, along with 100mgs. of Imuran.