The cables themselves don't get too hot, but the dongles themselves seem to get really hot. I'm assuming that's a known issue given the size of the heatsinks on them.
Unfortunately that's non-DAC copper cabling life it seems. They build them to work at the rated speed at the maximum rated distance (on the transceiver, not the spec) and none of them appear to link train to reduce the power output over shorter runs.
If you use a DAC they usually run cool, and optical is even cooler.
If you use a DAC they usually run cool, and optical is even cooler.