I only found out about Bitcoin a month ago, I only have 2 S3s for experimental purpose, I am not expecting them to ROI (ordered late (batch 6) and bought coins while they were 600 a pop). using them as heater for appartment, it is cold here already - 18 degrees during day outside.
yes, tried power supply swap. tried moving the units apart, using different power outlets, swapping pci-e ports (now they run all 4 pci-e ports connected) and what not.
the hash rate does sometimes (like the one 30 hour period I mentioned) drop 10% which is below the expected rate.

thank you for looking into it, I think this needs engineer to find the cause of the problem

here is someone reporting same behavior:
https://bitcointalk.org/index.php?topic=671189.3900
https://bitcointalk.org/index.php?topic=671189.msg8169759#msg8169759

edit: this is offtopic anyway, my question was - does restarting cgminer every 1 hour cause problems with pool shares?