A long time ago I noted that Billy absolutely hates to give up a pom-pom after he catches it. That is out of date.
Some where in there, I am not sure when, I learned to stand in front of Billy when he comes down to level ground from where ever he caught the pom-pom. This discourages him from wandering off. At the same time, he learned that if he drops the pom-pom, he gets to immediately chase it again. Now he generally only hogs the pom-pom if he's tired.
I also changed where I cast the pom-pom, and perhaps other subtle changes, but I can't really say what was important and what wasn't.
In any case, our routine for many months has been a very consistent cast-chase-catch-drop, repeat cycle. (There a lot of misses in there, but that's part of the game). Both of us are happier, and the mighty hunter is indeed mighty.