I keep most all my batting leftovers these days. I'll use the iron tape as I have lots of it on hand right now and as I cut my pieces off a finished quilt and I have the iron on anyway, I'll go ahead and piece them onto batting I've been piecing together. Once I get a decent size, I mark it with the size so when I'm looking for batting I check my rack for what sizes I have already before I go to my bolt of batting to cut. When there's more tape than batting I call it finished and toss it. That rarely happens though.