I re-use my Bounce Dryer sheets a couple of times then I have a bag I made for them to be stored in. When the bag is full, I give them a good soak in soapy water in the sink and then I dry them in the dryer. I have used them for applique many years and never had a problem. I do iron them before using & store them in a card board type photo box til ready for use.
I am probably washing them needlessly but just doing it to be on the safe side. ;-)