I buy them in quantities of a thousand. I separate them into ziplock bags of 100 and store them in a cool dark area. This way they stay clean and when it's time to cork I just pick out what I need and spray them off with some sulfite/water solution and allow them to drip dry a bit then cork.
They don't leak...good news but the downside is they do not allow the wine to breath. Don't know if thats a problem or not.
Anyway I love them. They remove so easily and don't break off and look good in the bottle.