I switched to the slush proxy, and it stays up for between one and three days at a time now. But then it will still *click* and shut itself off, requiring a manual toggling of the power.

[edit] I'm using the slush proxy with the -rt option to relay the vardiff changes along to the cube directly. I'm not sure if that may be one of the reasons it stays up longer this way; back with the bfgminer proxy it would do the diff filtering on the miner software rather than the cube (I think... if I am wrong here please anyone feel free to correct me)