Changed Medication From Pentasa To Imuran For Crohns Iletis. Is It Necessary ?

Had been on some strong antibiotics at the end of 2010, a few times prior to symptoms of stomach pain (not in lower right quadrant), and had more frequent bowel movements (not diarrhea). I was diagnosed crohns ileitis in April 2011 through at CT & Colonoscopy. Been on Pentasa for 1 1/2 years. Had a CT & colonoscopy today and it still showed aphthous ulcer, with some thickening of the walls of the ileum on the CT. Since being on Pentasa I'm asymptomatic - stomach pain went away and bowel movements back to regular schedule. Dr. now wants to put me on 50mg Imuran. Since I am asymptomatic and nothing has changed since 2011, is it really necessary? I would't have know about the ulcer still being there, but I asked if I could get off Pentasa altogether, so they did a CT & colonoscopy yesterday to see what was going on. Otherwise I wouldn't have had a colonoscopy until 2017. Can I take a wait and see approach and get off all meds or just stay on Pentasa? Not really convinced it's Crohn's since I don't have any symptoms. Male, 55 years of age. No other health conditions.