I am letting mine run. I never turned it off since last night. Still at three bars our of four. (However, I did have the mics disconnected for some hours. So I will let it keep on running with the two phantom powered sennheiser 8070s connected. We will see what it is at tomorrow.
Probably good to burn in the USBpre2 anyway.
Best,
AB
update - this morning it is down to two bars. I think someone may get more than 24 hours on this. Does it have anything to do with it being rated at 2.4 amps and only one unit connected to it (thought two phantom power mics).