I've also had it a little tougher the last couple of months. In the last two months, I've had only one trip that I've killed more than one coyote. On my best day I only killed two and I had to work for them. I believe I made about 8 stands that day.
On Tuesday morning I had a coyote howl a couple times but never came in on the first stand. Second stand I had at least two coyotes yipping and howling at me from what only sounded like a 1000 yards out and another one that was about a mile in the opposite direction howling at me and none of them came in. On the 3rd stand of the morning I had a rabbit distract a coyote I called into 50 yards but I was able to get a clean shot at him a couple minutes later.
Last month I called in 4 coyotes one day and didn't kill any of them. Probably my most frustrating day all year. 1st stand of morning the coyote "back doored" me. I took a shot as he was trotting away at about 150 yards and missed. I should have waited for him to stop but I was too confident in my shooting abilities. I was truly surprised after the shot to not hear the bullet thumb him and to see him run off. 4th stand had a coyote wind me from 200 yards out and I took a 350 yard shot at it as it was trying to get away and I missed. Both those were not extremely easy shots, so I wasn't too mad at my self. 5th stand of the day, I had a coyote come in and stop at about 100 yards and gave me a perfect shot opportunity and I somehow missed and then missed him 3 more times as he made his get away. By this point I was sure the scope on my 22-250 was off so I took 3 quick shots into a water bottle at 100 yards to check. All 3 were within 1/2" of my aiming point. 6th stand I had a coyote sit down and stop at 265 yards. I put the cross hairs dead center on the chest and shot felt like it would be good but I lacked confidence. The coyote's body language also looked like it would continue to come in to my calling. Sure enough, as soon as I started calling the coyote came trotting into 100 yards and then started circling to catch my wind. Every time it stopped, it was behind some brush so I kept waiting. I waited too long because it circled just wide enough to get my wind and never gave me a shot as it took off. That was a good day of calling with coyotes on 4 of 7 stands but a really bad day of executing the shot. I would rather call in only one coyote all day and make a good shot, than have a good day of calling and bad day of shooting like that.
About 3 weeks ago I made a short trip with time for only two stands. On the first stand I had a coyote howl at me but I gave up on the stand after 30 minutes. Walked about 400 yards back to my 4Runner and then as I'm driving past my stand, there is a coyote running off 200 yards from where I was calling. If I had waited just a few more minutes on the stand, I would have had a chance at him. 2nd stand that morning was a blank.
2 weeks ago I called in a coyote in the first 5 minutes of the first stand and then didn't call in another coyote for the next 5 hours. A week ago, the same thing happened. Coyote came in on the first 5 minutes of the first stand and then nothing for the next 5 hours. My shot execution was better both those days though.
There were also a couple short trips last month that I didn't call in a single coyote.
The challenge is what makes it so rewarding when they finally do come in. I shouldn't go out thinking I'm going to kill 5 or 10 coyotes in a day. They are very intelligent and have superior senses and physical abilities, I should feel lucky that I occasionally get one.