I see that Betterbee now has calendars that attach to mating nucs. They let you know when the queens will be ready without having to disturb the nuc. I've seen variations of these in queen rearing books but NEVER in any supply catalogs. Looks like a great idea.
you still have to know when you put the larva in the cells how old they are.
it takes little experence to know when queens are ready to emerge.
I think someone just found another way to get little money out of us.
no pun intended