can I also ask a question, it still has to do with round bales.
If you were to buy bulk of them in the winter and put them undercover, they could last for ages, right?
Like they wont go mouldy or anything just sitting there?
As long as your tarp them nice and tight, they will last the year. However, if it rains and they are directly on the ground, the bottom of the bale will get moldy and mushy. I don't really mind that little bit of hay going to waste. I just pull it off after I put the bale out in the field, or make sure that is the end on the ground (we roll them out by hand, no tractory ATM).
I use tent stakes to stake a tarp down to the bottom of the hay bales, with the stakes angled up. This allows for some ventilation at the bottom of the bales, but keeps the tarps closer to the hay, which prevents the wind from getting under the tarp. I only have one round bale left, with 9 more stored at my hay guy's barn (I pre-pay at the beginning of the season). When I have the rest delivered, I think I am going to buy smaller tarps and tarp each bale individually. My big tarps haven't been lasting very long with our high winds at times, and they are pricey. Buying 10 little tarps is cheaper if I buy them in bulk online!
Also, one horse will go through one 600-700 lb 4'x5' round bale a month, give or take, if there is NO grass to eat and they are on the bale 24/7. During the summer, one round bale would last me 2-3 weeks for 5-6 horses, but that's because they did have some grass to munch on in their pasture (not much, but enough).