Darknight,
My experience has been that coyotes can show up most any time of night. I do see patterns "sometimes" with particular coyotes. For instance, recently I had a coyote visit the bait site a few times, all in early morning, something like 4:00 to 5:00 AM. Every time it visited it would come around that time of morning. Particular coyotes seem to have preferences when they visit, but I have seen them on a schedule and then suddenly change and come earlier.
I have had a lot of coyotes hit the bait one night and then not return for several days or even weeks. You can never tell, and while sometimes there is a pattern, many times you can't tell when they might show up. I cannot figure why they would leave a bait site knowing bait is there, but they do and may not return for a while.
Trail cameras are your friend and it's best to check them regularly for any pattern. But also, if a coyote hits my bait site one night, then I try to stay at my cabin the following night and sometimes even a second consecutive night. I go early in the evening and get settled in before dark. I don't want to arrive after dark since I might spook one if it happens to be in the area. My most productive method is to stay at my cabin the following night once they hit the bait, but I have experienced many times when they would not return the next night.
When coyotes are in the area and actively hitting the bait, that is the best time to hunt. They may stay in an area for a few days and then move on for a while. They will return sometime later but it could be weeks. I currently have a good bait pile and it's now been close to two weeks since a coyote last visited. Go figure. It will most likely show up again unexpectedly, but may only come one night and then be gone again. That makes for some difficult hunting.
I have also noticed that coyotes tend to visit at certain time frames, though you can't always count on that, but I have seen it enough to keep those hours in mind. Good times have been around 9:00 PM, 11:00 PM and from 1:00 AM to around 5:00 AM.
Having said all of this, one thing you can count on is that you can't count on coyotes being consistent. Bait hunting is not as easy as most people think. It's actually a lot of work keeping a site baited and cameras checked, not to mention time spent in the cabin, as well as disappointments.
Just be prepared to stay the entire night when you do hunt, which means having a warm and comfortable place to lay your head for some rest.
Hope this helps.