Unsure at all really, but something I would consider is the freshness of the hay in the long run. After I get to about half-way through the smallest Oxbow Hay bag (orchard hay), Wick definitely can tell it’s not as fresh. It’s much less enticing for him as compared to the first half of the bag, just due to air exposure.

I bought a 20lb box of orchard hay for Thor, she went through it in about 3 months. But she is a hay monster and also wastes a fair amount so I would guess a 50lb box might last your two 3 months or more. I’ve never personally faced problems with hay losing palatability with time, but maybe it depends on they type of hay or how picky your bunnies are?

Good point Wick! Luna gets pickier when the bale is nearing the end. I buy the Oxbow Orchard 9 lbs. She’s 4.12 lbs., a messy eater, and a hay monster, so it lasts around 3 weeks max.

I bought one of those 50lb monster boxes once, and it lasted a while… I didn’t notice any change in their preference for it over time and it seemed pretty fresh till the end. I think having it stored in the dark, with a bit of air flow (cardboard box closed but not in an airtight container) helps it keep longer. I thought it was a good value, I just didn’t really have anywhere to store it, so I buy mine 20lb at a time now.

I suspect when you buy smaller bags at the store it starts off not as fresh, as it goes through all the pet store supply chains before getting to you vs. a bigger box or bale might come straight from the farm. Just a suspicion though

My monsters go through 20 lb of hay in about a month and a half.

I’m not sure how much 1/2 bale of mixed hay weighs, but that’s what I bought last month, fresh from local farms via Friends of Rabbits. Given that I was on vacation for a week, I figure that I’ll need a refill in about two more weeks. I store the hay in plastic bins, closed but not airtight, away from direct sunlight. The hay is refreshed twice daily in the litterbox and once daily in the hay rack, so that Panda and Fernando each get a daily ration of hay at least equal to their body volume, and even though they’re both enthusiastic hayeaters there always seems to be a good deal left over and soiled/wetted. I once bought two 90-oz. bags of timothy from Pet Supplies Plus when I was really low on my regular hay stocks; the buns loved it, but with two 3/4-lb. rabbits chowing down twice a day a 5 lb. 10 oz. bag didn’t last more than a couple of days. I still have the other one as emergency reserve.

I’m pretty sure mine get through about 1kg a week

About 2-3 months depending on the buns The bales I buy probably weigh in the range of 20-25kg depending on how fresh they are and I get at least 2 months from a bale for my greedy pair.