Torouter on OpenWRT shouldn't have its data directory in /tmp/
AIUI, Torouter stores its data directory by default in /var/lib/tor/ with /var/ being a link to /tmp/. This means that whenever Torouter is rebooted, Tor generates new keys and gets a new fingerprint. This prevents bridge clients from learning a bridge's new descriptor whenever the bridge changes its IP address. Tor also loses its state file with circuit build timeouts as well as previously written stats. Robert Ransom adds that bridge clients will think the bridge is MITMed and possibly shout warnings at the user.
My Buffalo router has 25.6M available on /tmp and 22.9M left on /. In theory, we could move Tor's data directory to /.