Well, for horses, old hay is better. I never feed them that summers hay until after Christmas, if I can manage it.
Hay especially, goes dusty. But if you have any left from this year, its quite allright to use next winter. Just make sure its stored in a dry place, away from damp floors, and walls. Straw, I find keeps better, and you can keep that longer without a problem.
I tend to feed the goats haylage off the horses big bale. The goats love it, and the llama does too.
If you were nearer, I would let you have some to see what your goats thought. I would post it, but not a good idea, it would not go down well with the postmen. That reminds me, my friend kept her ponies in her stable in the garden, and the neighbours complained of the smell of the haylage.She got a letter from the council. What did she do? Posted a wedge to the council man and told him he could see for himself that the smell was not horrible. Imagine his face when a pile of haylage fell out onto his desk!!!