Hi Phil.
The thing to bear in mind is that a swarm of bees is like a bunch of refugees - they're carrying all that they own in the world along with them - in the form of honey. And that honey is needed to make combs with, without which the colony is guaranteed dead in the water - and so must not be used up by needless flying around. So - that's why they send out just a few scouts, rather than search for a new home 'mob-handed'.
They will relocate their temporary position if they really must - (say) if they're seriously disturbed by something, or by somebody. But - in general, they'd much rather not. And if they can't find somewhere suitable within a reasonable time - then they may well start building comb in a non-viable setting, whilst they still have enough honey left for that purpose - such as within a tree canopy or under an overhanging branch. And if left like that (exposed, and in the open), they often perish.
Combs aren't just some convenient place to hang out - they are an essential component in the life of the honeybee - they MUST have combs, else they simply can't survive. Which is something the purchasers of package bees and the users of plastic combs might do well to consider a little more carefully perhaps ?
LJ