Take every last crumb out of luggage before storing it -- every tennis sock, receipt, tourist map and hairpin. Anything left in luggage may rot, mildew, tear liners or create some nasty surprise for the next time you grab a bag to pack right before a trip. Never leave worn clothing or dirty laundry in a suitcase. Your luggage will become a petri dish for bacteria and mold and you may never get the smell out. One trick that helps to keep luggage smelling fresh is placing a dryer sheet inside each suitcase when you aren't using it. The sheets inhibit mildew and definitely banish any unpleasant odors.
Creative Storage Solutions
Nest your unused luggage. Clean it out, air it out, and then tuck the smaller cases inside the larger ones. Keep all travel gear, such as neck pillows, net laundry bags and other travel cleaning and comfort items, in the luggage as well, but don't store anything liquid or gel. Tuck the nested luggage on a top closet shelf where it will stay dry and benefit from some circulating air. If the attic, basement or garage is dry, wrap the luggage in an old sheet to keep it dust-free and stash it out of the way. For vintage luggage, interesting mismatched luggage or reasonably attractive luggage, an artful stack like a pile of books under a side table or in a corner can be a practical sculpture. Cool, hard-sided luggage makes an interesting end table to hold a lamp and even provide extra storage in a small home. For luggage you'd rather not show off, store it under the bed.
Tempting as it might be, wrapping the luggage in plastic to protect it isn't a good idea. The plastic will prevent air circulation and trap any dampness. A few days of high humidity will turn your luggage into a mildewed artifact. If you need to keep dirt or dust off stored luggage, an old duvet cover will protect it without smothering it. If you live in an apartment and have storage elsewhere in the building, be sure it is climate-controlled before trusting a storage bin with your expensive luggage. Building basements are notorious breeding grounds for mold and mildew. That may not be a problem for your bike, but it could be fatal for your travel bags.