[vid]

It is random, it depends on how familiar the editors are with the area where the requested building is located, and how much information the submitter has included in the request. Since all editors are volunteers, it's also subject to the time they might have available to respond to the requests.

If the buildings that have been in the queue for a long time are all from the same general area or submitted by the same user, it's likely that no editors from that part of the world are active at the current time.