A few things I didn't see mentioned here I have experienced.
When you wait 24+ hours to introduce a cell or virgin, you obviously allow them time to make their own cells. Such as in my mating nucs that have been queenless for 24+ hours, when I install a virgin, I go through the nuc and remove any started cells.
But there are times that marked virgin is successfully mated, has returned and is laying when she disappears and a new unmarked queen is found in the nuc. I can only explain it by assuming I missed a wild queen cell, it developed while the installed virgin was maturing and getting mated, When the cell hatched, the new virgin-being the killing machines they are- did in the young newly mated queen. This has happened several times to me and that is in a small mating nuc. With Larger nucs your chances of missing a started cell are greater.
(All my virgins are marked when hatched out of the incubator. The only unmarked queens had to be hatched out from self made cells)
So if you give the nuc enough time to possibly make their own cells, you run the risk of missing a cell and the same thing happening. A waste of a few weeks and you run the risk of letting the nuc dwindle. You'd be just as good making a walk away nuc. But if it is getting late in the summer, it may make the difference between success and failure for that nuc to build enough to overwinter.
I guess my point is, there is a danger if you wait long enough for them to get their own queen cells started. Sometimes a newly started cell is no more than a cell only slightly enlarged with more royal jelly..not even elongated yet and covered with bees. It would certainly pay to go back a few days later and recheck for rouge cells again when they would be bigger and easier to spot. Depending on how many nucs you start, that would mean another full day of labor or more.
Also, if a nuc is queenless for very long, the eggs will disappear. Whether they clean them out or cannibalize them, I am not sure. That's a loss as well if you let them do that.
They know they are queenless pretty fast when you remove the queen. Personally I wouldn't give them more than a few hours before placing the cell, and wouldn't hesitate to put them in as you make up the nuc.
It's how you handle the new nuc that determines it's mood as well. Make them up and close them in and they'll get heated and ticked off and could very well be hard an a queen cell. Make them up and let the foragers fly back to the old hive and they are receptive young bees left to accept your cell. Just gently brush in enough extra young bees from a frame of open brood to allow for the loss of the foragers.
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