Gandalf also seems in need of sustanance in the Hobbit after following Beorn's bear tracks(mmmmmmmmmmm....bearrr track...).
He wouldnt even talk untill he had "eaten two whole loaves with mounds of butter and clotted cream, and drank a full quart of mead". This seems to point toward him being limited by physical need. We could also say, "Do mair need to sleep, do they need to drink." Mair in general, probably not, but in the case of the Istari, almost certainly.
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There long the golden leaves have grown, upon the branching years, while here beyond the sundering seas, now fall the Elven-tears...
but if of ships I now would sing, what ship would come to me, what ship would bear me ever back, across so wide a sea?
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