if my juice gets low (it's a favorite) and I am going to refill, do I just refill, even if it's slightly darkened? How about a lot darkened? On ones I could care less about, i just dump em and pour in new. But on ones i like i would like to vape it all before buying more. what if I saved "used juice" in a little bottle? Any advice will help. I want to save money but I want to vape good flavor so I continue to love it. I may have posted a lot but I am still a Noob, HELP! lol