Bait hives....how long?

[Hux70]

So a 2nd swarm has arrived at the bait hive today and appear to have taken up residence. The 1st swarm went in, came back out and spent the night bearding underneath. These were caught and rehomed. In the bait box there are only 3 pretty grubby old frames of wax and an empty frame. How long should I leave them before removing them to a new hive?
This is my 1st swarm using this method. I usually spend most of May balancing precariously up a ladder with a cardboard box

 

[Beesnaturally]

I'd be tempted to at least move the grubby frames aside in the hope that they won't use them, and get them out when you feel you can. Depends how grubby they are I suppose. I'd want to be happy they have enough room to want to stay, and they aren't going to think they might get too hot later.

I reckon after 24 hours they will stay unless they can think of a good reason why not. I've very rarely lost them once they're in. But I did once lose a giant swarm that I housed in just a national brood box.