First, back to the fpl site, where you'll find that the inverse square
rule
applies. Double the thickness, almost four times the time to equalize.
Believe they say "more than three." Second, evaluate the grain
direction. I'm presuming you have heartwood, but not boxed hearts, or you
might as well plan on burning them this fall.

Heartwood yes, but what is "boxed hearts"?

I also have several boards completely sapwood. I thought it might be fun to
have "white" walnut.