If I keep an iPod nano attached to a power source, and keep it playing music (without any actual output–just as a way to keep it from going to sleep), will it “hurt” the player in any way?
There’s always mechanical wear-and-tear. If you have an iPod with a spinning hard drive, it’ll eventually wear out. If you have a flash memory model, those flash chips are only rated for X number of reads and writes (X is an appropriately huge number, but still finite).
Eventually, everything will wear out, and running it 24/7 will make that happen sooner than later. I don’t know of any special damage you’d be doing to it, though. It’s meant to play music, and that’s what you’re doing with it!
There’s essentially no upper limit on the number of reads for Flash memory. Only writes are wearing. So, running an iPod continuously is OK.
I suppose that’s true for flash. I still think the iPod itself is experiencing wear-and-tear on its inner components… there’s no way it can run forever. 
Is there any heat involved in this, and if so, could it eventually lead so some kind of degradation?
But, if the nano is not connected to any output, is it really playing music?
If the intent is to keep it from going to sleep, what are you accomplishing? The screen dims to black, even when playing music.
Nope. I discovered by accident that when it’s plugged into a power source, it stays on while “playing” music.
My question is…why? iPod’s take moments to “wake up” what are you accomplishing by playing music constantly without output? Keeping it plugged in constantly to use at an instant to play music on a system I can see, but keeping it awake I don’t.
I don’t own an iPod and don’t know what kind of power management they have, but would keeping it plugged in to an outlet and not cycling it through a discharge/charge cycle every so often eventually render the battery ineffective?
I’d worry about battery life first and foremost. (And given how hard Apple made it to replace an iPod battery, that’s a bigger issue than for many portable devices. I’ve done it and … it causes me to say bad words.)
Keeping a battery powered device plugged in and trickle charging reduces its lifetime. Heat and the chemical changes of charging are not good for batteries.
Some devices are smarter than others in stopping the charging completely once it is fully charged, but based on the heat put out by our two iPods when connected, that is probably not the case here.
To keep the nice analog clock constantly displayed…
Walmart will sell you a very nice analog clock for $14.95. It’s even atomic.
In fact you could buy 7 of those clocks for the price of an Ipod Nano.
Probably not a problem, since manufacturers usually quote a minimum data retention time of 10 years. The thing is, that is at the maximum rated temperature and it increases exponentially at lower temperatures (the oft-quoted “double/halve lifetime for every 10 degrees C less/more” rule, although it isn’t always a doubling and may be more or less); see this paper for examples (by testing at extreme elevated temperatures, they can extrapolate the lifetime at lower temperatures, without having to actually test them for decades or centuries):
For a low-power device like the IPod Nano, the temperature probably isn’t going to be much higher than ambient, say 25-35C. Write cycle life also isn’t likely to be a problem even if you refreshed it every single day, which would be over 27 years for 10,000 cycles, which is also a minimum as well (this is really only an issue in systems with intense write activity and/or very long lifetime).
By far the most likely limiting factor on lifetime, at least if you plan to ever use it on battery power, is the battery itself; even if unused, it will degrade and become unusable after a few years, especially if it is kept at 100% charge all the time (degradation in lithium-ion batteries is dependent on temperature and charge, in addition to charge/discharge cycles).
When I plug an iPod into iTunes, it can tell me how many times I’ve played each individual song, so it must be writing that information somewhere while the iPod is playing. It also keeps track of where you were so that if you turn it off and turn it back on, it goes back to where you left off. It also keeps track of the time of day. So I believe there is a bunch of memory writing going on even if you are just playing songs.