Short of actual emergency surgery, this is an almost impossible question to answer. Only you can know when you have reached the end of your tether. For me, it was in January 2013 around my birthday. I had a flare-up which was the final straw. I say 'flare up', but the only thing keeping me from emergency surgery were steroids. It had reached a point where I could not come off steroids without suffering acute abdominal pain and ending up back in hospital for more IV steroids. My colon was toxic. I had at least one incident of toxic megacolon, possibly more. The steroids were a fantastic symptom-masker but without them I was unbearably ill. Remicade and Humira hadn't done a thing.
I could have limped along on high doses of steroids for a couple more years, no doubt. But I don't think anything could have saved my colon by then. When it was removed, the pathology showed severe disease throughout - there wasn't one healthy bit left anywhere.
In your case, I'm not sure what state your colon is in or what your quality of life is like (not great I should imagine). I would seek a second opinion from another colorectal surgeon. But before you do, take a look at this site and see what you think.
ostomycure.com/The important thing is, if you decide to go for a stoma now, then nothing is stopping you from switching over to the TIES implant at a later date if/when it becomes available.