Just a small update. The unit is still running great, only once I received an idle notification from BTCGuild. Somehow cgminer crashed, but I could just click on "Start" again, didn't even need to reboot the unit.

As of now:

System Uptime
74 day 23 hr 3 min 58 sec
CGMiner Uptime
21 day 1 hr 24 min 20 sec