i am hanging a ceiling lamp which came with an cord set only rated 60W -- insufficient for my purposes. poking around in my parts bins, i found a rubberized E26 socket rated something like 660W, but labeled "FOR TEMPORARY USE ONLY". what does this rule mean, and can i use the socket anyway?
It likely means that it is NOT designed or constructed for CONTINUOUS use and/or to be built INTO some kind of fixture. It can handle the heat dissipation only when out in the free air, and with intermittent use. Perhaps no more than 2 or 4 hours at a stretch, etc.