as long as you want. Keep them in an airtight bag/container and open it every other day. If the leaves have dried up and the bud still seems dry, just add more leaves.
Its really up 2 you how long you want them in there for. The longer, the more moisture as long as the leaves are still moist
I think the leaves would have the same emount (if not more) moisture within them and would not make my bud orange tasting either, i would want that if it was for personal use but this is for retail purposes only. I did use a banana peel one time on some crippy and it made my shit taste like banannas and it was really moist within a day! I would recommend not to use this on crippy though because of the cristilized thc on the buds. I was stupid and high!