Instead of having either an "on" or "off" version of a lamp (placed from units>empty>objects [lamps]), It would be much better to simply have a single version of each.

Instead of having to place a separate lamp to turn it on, double-click and edit its options like you would any unit. There would be 3 options: off, on, and "auto", which would cause the lamp to function like a static one (on at night and off during the day).