After running 10+ m0n0wall gateways on Wrap and Soekris hardware that
never required rebooting over a period of several years, we installed
one recently that has hung twice in 2 weeks.

The biggest difference is the sheer amount of traffic, much of it P2P.
 We have traffic shaping on, but no vlans, no captive portal, not much
at all.

What is the latest thinking on the most stable version to run in this scenario?

I just installed 1.23b4 and enabled the Wrap watchdog support in the
hope that it will help. All comments welcomed, and I'll report back if
it seems to stay up (usually takes about a week to hang).

cheers, michael