Let me qualify my comments:
A week after buying these 2 hives, i was hit by a car, spend time in hospital and in a sling. So despite putting a super on before I couldn't manage these hives for 5 weeks. right in the middle of swarming season. So I blame it on poor management.
Yes the hives were very full, and already had queen cups but didn't swarm until about 6 weeks after I got them home. I like to think that if i had been able to change around the brood boxes and create a sense of space, this wouldn't have happened.
Having said that, it was unknown how old the queens were, so I have decided to requeen them on Nov 15.
If you buy, i would suggest requeening if you can get your hands on some.