Well, after the units started acting up, I did unplug everything and let them sit for about an hour, and then only put the power plug back and none of them would boot up. What I would get is the flashing yellow with the usual Netgear splash screen on bootup, and then green for 1 second while it attempted to display, and then a blank/black screen and continuous flashing yellow for over 5 minutes.
However, after 3 days now of sitting unplugged, I did the same test and now all 4 of the units power on and work fine! They behaved as if they were new out of the box and forced me to run initial setup again. So it seems something is building up in them over time... which is why I tended to lean towards the capacitor theory. Actually, I did get the "your netgear has crashed, do you want to send data to netgear" and then it ran setup.
BTW, dumb question. I am running the original 3.0 stock firmware... and I came across a new 3.2.27 version (not published on netgear's downloads). Can I flash from 3.0 to this version, or do I need to flash in succession by first flashing to 3.2.16, and then .27?