Clean your vintage satin pieces before storing them, even if there are no visible stains. This is especially crucial if you have worn the piece for any length of time, as even a small amount of perspiration can yellow dramatically in storage. Do not attempt to hand-wash or machine-wash satin, since any contact with water will ruin it. Take it to a dry cleaner, preferably one that specializes in vintage clothing.
Fold vintage satin for storage, and wrap it in acid-free tissue paper; the acids in regular tissue cause yellowing over time. Place the wrapped piece in an acid-free box. If you use a plastic storage box, don't seal it so it's airtight; a little bit of circulating oxygen is good for vintage fabrics. Store the box in darkness.
Remove the vintage satin pieces from storage once a year, even if you're not going to use them, just to unfold them, air them out, and refold them differently so they don't develop permanent creases.
Freshen pieces that have been in storage with steam before wearing them. Use a steamer designed for clothing. When the steam starts to flow, hold the nozzle near the satin and move it back and forth slowly, enabling the steam to loosen folds and wrinkles. Don't let the nozzle touch the fabric, as it may leave water spots. If you're not confident with a steamer, have a dry cleaner steam it.