are ready to be walked out the door the moment you notify.
I haven't yet been walked out the door, but I've always been prepared for it. You never know when a manager/owner might subscribe to the philosophy that it really doesn't do any good to keep an obviously less than satisfied employee around.
"But I'm too important, too much to hand over, they'd never do that." And if you died in a plane crash tomorrow? They'd manage. Might not be an ideal transition, but they'd manage.