While thinking about implementing a cache in chan_iax2 guess what I found. I will add a note to the wiki, but I found below in a iax.conf If someone could explain why I would want rtignoreexpire it would be great and in reading the code rtnoupdate seems not to do anything.
; Cache realtime friends by adding them to the internal list
; just like friends added from the config file only on a
; as-needed basis.
; do not send the update request over realtime.
; Auto-Expire friends created on the fly on the same schedule
; as if it had just registered when the registration expires
; the friend will vanish from the configuration until requested
; again. If set to an integer, friends expire
; within this number of seconds instead of the
; same as the registration interval
;rtignoreexpire=yes ; when reading a peer from Realtime, if the peer’s registration
; has expired based on its registration interval, used the stored
; address information regardless