In my latest game, the random monsters respawn constantly. The Debug.err file (http://pastebin.com/f43e818ad) looks like this:
DebugMessage: ValidateDevice::Reset
DebugMessage: ValidateDevice::Reset
DebugMessage: ValidateDevice::Reset
DebugMessage: ValidateDevice::Reset
DebugMessage: ValidateDevice::Reset
DebugMessage: ValidateDevice::Reset
A couple of thousand times. I went around the map a bit and killed a variety of things, but it seemed to hold up everywhere. The sovereigns died and stayed dead, though.