I save some 3 or 4" strips, incase I need to add a small strip down a side or across a batting I need to use.
I have sewn strips of poly batting together, to use in a quilt sandwich. I have made three or quilts like that, it has been a while. Not my favorite activity but, those scraps cost as much as the bigger piece did. I used up a lot and cleared the storage area for more batting.