I'm up to 12 days at this point, but it was longer (a month?) before I did some re-arranging of things and needed to unplug the unit.
I have an AppleTV that's wired, and all the computers are on wifi, so we end up stressing the mdns a fair bit. It seems solid, although all the devices get confused about having other devices using their name, and increment theirs (the Apple TV is up to 1344).
Everything seems to be going well, though. But it's all still just ipv4 (I need to deal with comcast and getting their router into bridge mode, it's not just a modem at 192.168.100.1, it's a full blown router).
-Aaron