...the drives in question had been copying data non-stop for 15 hours or so,...

Your drives are warm from the constant copying, no doubt about it. I imagine with regular Empeg use they will be even cooler than the previous drives because they operate at lower power. (though I don't think it will be possible to feel the difference)
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Riocar 80gig S/N : 010101580 red
Riocar 80gig (010102106) - backup