Bluntcrush
Director of Vapor Research Labs™
Depends on what kind of repeated usage we're talking about. I tend to medicate all day and it usually lasts me a day. That's using a drop per oz. of water. You'll know when it's time to change the water. It loses it's color and gets sort of gross.
I generally use a freshly cleaned tube for about a day and a half. (vape all day too) I noticed though that sometimes there are some "cookies" floating in there when it's time to clean. I was thinking that someone should try to find a way to process the used distilled water (including cookies) and make some kind of new THC soft drink I'd call mine "couch juice" Make it a berry flavor add anti-oxidants and watch the dead presidents start rolling in!