When they land, they form a cluster temporarily in one area and can stay there from a few hours to a several days before moving to a new location.
During this period the scout bees are busily sourcing a new location to set up the new home and several factors are required for the swarm to agree to move on.
As a general rule, swarms are not aggressive as they are not protecting their home - they are looking for a new one. Also they have full stomachs of honey which makes it harder for them to wrap around their abdomen to sting. As I mentioned, this is only a generalisation as I have personally experienced some extremely aggressive swarms so don't be fooled thinking it is safe.
We recommend you ensure children and animals are kept well away from them and do not interfere with the Swarm as it makes it more difficult for removal and it can also aggravate them. thanks