
Braer Bear |

I was actually searching for what happens when you polymorph with a Ring of Sustenance. Given the answers here and a re-read (ie. it's about keeping the ring attuned to you), I would think in that situation it would also keep functioning without another week of re-attuning. Mind you, just like the anti-magic field, it would not actually function with you polymorphed, assuming the usual "your stuff transforms/melds and doesn't function while so."
The wearer will still WANT to eat, drink and get a full nights sleep, but they won't need to. Otherwise putting this on a guard beast would make the thing too content and lazy to do its job.
I can't completely agree with this. For one thing, it is based on Create Food and Water. I would think that it would curb your hunger. Also, I would think you would be finding yourself waking up after some period of time proportional to your normal sleep habits. Nothing says you can't eat more, wouldn't be tempted by tasty food, wouldn't like to drink mead all evening with friends, or want to/not be able to sleep all day long, though.
Your guard beast reference though... well... sounds very much like you are looking at a particular situation, saying it wouldn't be to your liking, and saying it therefore can't work that way. I don't agree. While your guard beast would, in my opinion, still value tasty treats, a Ring of Sustenance should keep him relatively content as I argue it should keep the PC's so. That doesn't necessarily mean he'll be all lazy and napping all the time. I would say that depends entirely on the beast in question if it did happen. Mind you, it would make it for a highly amusing if the low level PC's could just stealth by the sleeping beasts because they are that way before later in the story the NPC figures out whom can get the rings and whom he has to feed by minion.