It is a good idea.
Back when my now father-in-law was the county attorney, he had a few enemies to say the least. On two seperate occasions, someone burnt his hay pile. The last time, he was trying to move some of the bales to minimize his loss. Got the tractor high centered on a bale and couldn't move. Tractor burned up before the fire department got there.
I believe most farm plan insurance policies cover hay loss up to a limit. I know my policy will cover losses up to $5,000, anything above that will have to be taken out seperately or in addition to. Needless to say, $5,000 wouldn't go very far on your 550 bales. I would look into it. My brother and I never have, but we put about 350 bales in one area, which is about half of our hay. I have thought about it, just never done it. Might this year with the cost of hay.