Best to append in results from all cameras - e.g. one camera only sees the front of the sofa, or only peeks through a doorway into another room, while another camera sees behind the sofa or actually goes into the other room, well the Cache from the first camera won't have all the detail for behind the sofa or in the other room.
(EDIT - or separate caches, one for each camera, rather than one that appends the info needed by them all. Not sure if one is a preferred solution to another technically, probably comes down to four smaller caches or one larger cache and which you prefer to store and work with)