You'll find many opinions. . . .I think there is an ongoing thread in Let's Talk Kindle. . .but at the end of the day I think it's up to you. My understanding is that the device doesn't use any power while asleep, though if you have WN on it will 'phone home' every so often to see if there's content to download. But if you keep WN off, of course it won't even do that. If it's off, it's off. . .
So, the answer is: personal preference. I leave mine (K1) plugged in and asleep all night so my newspapers show up on time. I've never turned it off, I think, though I occasionally do a soft reset to clear any gunk in the memory.
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