Evidence base - Public forum - Planning Advisory Service (PAS)

This is probably one of those 'how long is a piece of string' questions, but when should the evidence base for a Local Plan be reviewed? More specifically, how long before we update our SFRA, Water Cycle Study, GTAA etc. when our Local Plan has suffered a set back whilst we find more housing land in conjunction with our sub regional partners? Moreover, should we be undertaking joint studies given that we are having to consider further overspill from the adjacent City than we had allowed for?

Thanks for any advice