It really depends on how many different fabrics are in a collection. Layer cakes and charm packs can also vary as to how many there is in each. I just used a Mod a charm pack that had 42 pieces in it but 6 were duplicated. So there were actually 36 different fabrics but withe 6 duplicates made the charm pack 42 pieces. This was a charm pack of a fabric line that came in 3 or 4 color ways so it was easy to get 36 different fabrics - same print different colors. If I was you ( and I applaud you for using up that stash!) I would choose 21 fabrics and duplicate them.