They aren't really cached. Routes are kept in the routing table as long as peers are responsive, if they stop responding to hello's or a link goes down to direc

They aren't really cached. Routes are kept in the routing table as long as peers are responsive, if they stop responding to hello's or a link goes down to directly connected peer the routes are removed (or replaced with a less preferred one). While its possible to configure a router to keep routes in the table for a peer that is down for some time its typically not used unless you have a good reason for it.