My A4 running 1.22b5 (I think its b5) currently has had its wan connection open for "51 Day 5 Hour 41 Min 39 Sec" (and increasing, obviously).
But, I'm sure "my setup" has little to do with why its so. I've got a static WAN port to another internal-network range, my wireless is off (location of router makes wifi useless, but I got it for gigabit anyway).
I know if I try to change the ntp server, the thing crashes (in an infinite loop, as best I can tell its because it tries to update NTP while doing the uplink measurement). I recall (approximately) 2 months ago when I updated the firmware that it gave me ABSOLUTE HELL about "measuring uplink speed" even -AFTER- I'd disabled the setting in the menu to do so. I know that if I turn on DNS relay I get more mdns resolution failures than with it off--but in my case turning off DNS relay just means that it hands off the IP address of the upstream router (also in my larger network) for DNS, which isn't really a problem.
Effectively I only use the thing as a logging firewall + DHCP server for this subnet. At this point things *SEEM* to have become stable enough to be acceptable, even though mdns occasionally fails for no reason (which I've now been attributing to OSX being confused by the double gateways).
But, I assume the most significant difference between my setup (aside from the uptime) and anyone else's that isn't working is the disabled wireless.
I still wish the 655's DHCP server behaved more like the one found in the DI604/614 router(s) however simple/broken they were they allowed machines connected though wireless and wired to switch connection media without dropping connections (I'm not sure how, but the DI604/614 did hand out the same address to both interfaces, and somehow between OSX/Linux/Router they kept it straight as to who was connected to where or whatever). /end tangential rant/
That was alot longer than I'd originally intended to write, oh well. Hope some feedback on a setup that seems to *work* (as screwed up as it is) might help somebody somehow.