The forum has been awesome helping me so far so let's hope for luck again!

I know that you have to get the keys or vouchers (or whatever you want to call it) to get into the Ring of Flames/Lamp of Flames/Tower of Kasa. It's the Evil Eye, the Wings of Light, and Kasa's Command. So my question is:

When you use the vouchers, do they disappear from your inventory, or do they stay there? And if they do disappear, are the quests to get them repeatable?