When you freeze the solution, it doesn't really freeze it, it helps to make the acetone nonvolatile so it doesn't evaporate very quickly. As far as changing it, it needs to be refilled every 6-9 months or so. Not all that often, and you can just add some water. I usually redo the ZEN POTION every 8 months, inbetween I just add a little 50% Antifreeze 50% water mixture to it.