Do food items refresh? Can a certain food item ever be eaten by a certain pet again, or can it never be eaten again? If it can, how long until I can feed it to the same pet again? Help would be appreciated.

You can feed a pet 2 of the same food item immediately. The "They've eaten this before" note is mainly to help people going for the gourmand achievement, which only counts new foods the first time they're eaten

Thx so much!