Winter kings are kings that stay local. At least that's been my experience here in Ketchikan. They still seem to be in one place or another at specific times. I've had no luck looking for them on my own. But that's what the charter people get for isn't it?
You should contract a charter captain in the area you'd like to go, before you go, for better details.
But if you're going in the spring, they aren't winter kings anymore are they? Those are the kings that are making their run.
For some reason, Canadians seem to refer to them as spring kings, no matter the time of year.
I hope you do well. Those kings up in the Kenai are the biggest one's in AK. Good luck.