Sure Shot, Most coyotes are judged by their size for age. I don't think many live past two or three anyway. They get hunted and trapped pretty heavily here. Both by sportsmen, trappers, and government predator control folks.
Early season is the best time for both numbers and fur quality. After December, the Government trappers start flying and shooting them from planes and placing M-44 cyanide traps. This is the time of year the ranches start having lambs and calves. They put a lot of political pressure on the Government guys to thin them out after Christmas.
The surviving coyotes get pretty smart pretty fast and are hard to call after that.
Besides, after Christmas, they start rubbing and their fur isn't very good anymore.
I think they den in the spring and have litters, so early in the fall, there are lots of dumb young pups running around and the adults have forgotten what predator calls sound like. The fur is prime this time of year, also.