I've never owned kingsnakes but I do own a cornsnake.
Before she sheds, which is usually once every month/month and a half, her colors will turn very dull. She is normally a bright red color but during the first phase of the shedding process she turns a dull pink.
I don't think corns or kingsnakes get pink bellies, but you could look for it as a sign.
After the dull phase has begun, a few days later their eyes will turn blue.
A few days after that the blue will clear up from their eyes...and a few days after that they will shed.
Like I said, I've never owned a kingsnake, but I think the process is pretty much the same for most snakes.
Don't worry too much about how often yours sheds. They all kind of go at their own pace, I think.
Shellie