If you are in remission on the meds you are on then stay on them. You are on the mildest of the meds for this disease and can stay on them long term.
I would really question a doctor who wants you to purposely go into a flare in order to try a more "modern" medication (and insurance may or may not even approve it if you haven't tried some other older types of meds). Is the medication Xeljanz? That was recently approved for UC and based on conversations I have had with a couple docs I suspect that the drug reps are really pushing it as a wonder drug. For some it is. But do some research and you will find it doesn't work for everyone.
If it ain't broke don't fix it
60 yo female diagnosed w/UC to mid transverse 1/1/13, now UC or Crohn's colitis. Remission on Entyvio 10/2016-12/2017 before losing response. Had response to Humira with loading doses in Nov 2018, but then lost response. Current meds: Remicade 3/15/19, Asacol HD 2 Tabs 3x/day, Capozide 1/day (hypertension). Dexilant.