I've owned a pair of KRK VXT6 monitors for about a year now. I'm very happy with them overall but they do seem to get rather hot after periods of extended use. Not burn your hand hot, but enough to make me wonder whether it's detrimental for the speakers.
I've consulted the manual and there's nothing in there regarding overheating. I guess common sense should prevail. I live in a hot climate (Bangkok) but the room is air conditioned and if anything, it's too cold.
Some days they're working, non-stop, from 7 a.m. to midnight. There are no heat sinks on the back of the cabinet.
So, without wanting to be too subjective here, and there any rules of thumb regarding how long speakers may be used before they earn a rest period? For example, in a proper studio, would a pair of monitors ever see 15-18 hours use?