Here is the definition of remission: "14 days without insulin and normal blood glucose values. Most remission cats are able to stay in the normal range all of the time (50 to 80 mg/dl), although there are a few cases of sporadic higher and lower BGs. Don't stop feeding low-carb and try to avoid cortisone if possible.
Although Toby has seen some lower numbers which is good, he is not ready to be off of insulin yet. There are a couple of dosing methods in the Prozinc forum. You might want to read about them and chose one to follow. The dosing methods will tell you how and when to reduce the insulin dose down to the point when you can start the 14 day OTJ (off the juice) trial without insulin. Of note, a cat needs to be regulated before remission will happen. Our goal here is a remission that lasts.
As for the statistics, our saying is ECID - every cat is different. In general, the sooner you can get a cat regulated, the greater the chances of remission. But many of us have not known how long our cat was diabetic before diagnosis, which adds to that time. Also, there are underlying conditions that can cause insulin resistance and those also need to be treated if they exist in a cat. Even something as simple as needing a dental and inflamed gums can make regulation harder. As for the question about switching to low carb wet food, again, I have seen a wide range of time frames. Some almost immediate, some not so much.