I don't mind recuperating the last bit of a liquid in a spare bottle. I only
vape fruit flavours, and the result is quite nice - right now it's a mixture of blueberry, watermelon, juicy peach and passion fruit, the four flavours I've been using in the last couple of weeks. They're all about the same strength, and work together like a fruit mix punch.
I wouldn't do it with things I didn't like, though.
I have a little 10 ml plastic bottle with a long needle tip that does a good job of siphoning off the last drops in my
tank, then storing it. It's just
vaping left-overs...