I took the `pause' out of the cgminer statement(s) so they'd loop if necessary, and I have restarted the two instances that have been dropping out. Everything looks normal so far, I'll report back on this, say Monday or Tuesday.
So... naturally both cgminer instances have been chugging away - and both show the start date as last Friday - no looping required... Maybe we scared them!
At any rate, I'll keep an eye on these two rascals.