How long does it take for a full pet to get hungry?

It ... is difficult to say because it breaks so often. I've fed Cibophobia to full before bed and woken up eight hours later and he's only gone down a couple of points.

if pet hunger is working like many users think it should, then about one piece of food per hour. Weird effects like pets not getting hungry for days, this happens too. I chalk it up to some of my pets are experimenting to be cold-blooded, but like said it's really a site error.

I shove food my pets need to eat into my book shop and then when it appears that they are hungry the shop sort has a "food" category and most foods don't look like books so if there's a category error in the system somewhere I can still find it. Then I take the items out and do a feed. This stops me from putting food into my shop and accidentally selling it or clogging my inventory with "need to eat this" items.

Thanks a lot!