If you're using a system image to reset/re-install the OS, the use of the system repair disc is a bit redundant. Generally the system repair disc only pertains to an OEM system. Where as a retail OS is the system repair disc.
Sorry, but I don't understand this answer. In the event of a crash I can boot from a repair disc (just as I can from the original installation disc) in order to restore from the system image. Having said that, though, it seems obvious that the repair disc does not need an update for each new image, so that is an answer in itself.