I would recommend trying the Asacol. It usually doesn't have side affects and it will keep you in remission. It's worth a try - it's nothing like prednisone or Entocort.
I don't know when you're in 'remission' either, other than you feel better sometimes and worse other times. When I'm 'feeling better', I assume I'm in remission, although some of the side affects of Crohns never go away anymore for me (fatigue, joint pain, left sided pain, in particular). I don't really trust the clinical tests to tell me I'm in remission because there have been several times when I've felt terrible, yet the tests (colonoscopy, barium Xrays or abdominal CT's) show nothing.
Learn to listen to your body - it will tell you more than any doctor or test. And take your meds...! That's my advice, anyway. Good luck!