I VE done it, with both control v2 and mix, 7/24 for about one week, then both have problems. Mix with texts cutoff, control burned, no more power. Fortunately they are in warranty and had been replaced quickly.
Not sure it's 100% related with the fact that tey are powered on 24/7, but I prefer power off them when not used. My retailer even tod me artists series are entry-level compare to c series (of course i know his strategy is to sell me more expensive AVID controllers...), so keep them powered off when Not used.
