I'd like to see some stats, or even some conjecture, as to the longevity of a bridge, and what it means for the bridge to be born, be used, and eventually be blocked.
I understand the mechanisms used to slowly feed bridge information to people who request them, but even that slowness can't keep them from eventually being discovered and blocked.
It seems that a reasonable question might be: for a home user, with a static IP, planning to contribute to Tor, which is most useful: should they just be a bridge; start out as a bridge, and then eventually change to a relay; or immediately sign on as a relay? Given some responses to this, might it make sense to construct a tool to tell people when their bridges should change to relays?