I had my first quilt long-armed last summer. He did a good job, but did not return the excess. I had sent a king size batt, 120 x 120 inches. and expected about 120 x 30 inches back. I called them, and it wasn't right away. I had to stew a little first LOL. They said they still had it. The next time I was there, I forgot about asking for it. So I called them and asked if it was still there, and it was. They had just had a big blow-out sale, so I was concerned. I did pick it up later. It was stuffed into a bag, so I had to smooth it all out and roll it up so I could use it again. I butt those ends together and use as much as I can in charity quilts, and in family quilts as well.
I make pillows with all the little itty bitty ends and pieces of batting. I have a box under my table near the sewing machine, and whenever I have a little piece of batting in my hand, it can go easily into the box. Then once a year or so, I sew up a pillow ticking and stuff it. My local food pantry gives them away.