It is perfectly acceptable to mix bottles of Perpetuem or Sustained Energy ahead of time, though for maximal potency we recommend consuming the pre-mixed bottle(s) within 48 hours’ time once mixed. Freezing the mixture is also completely acceptable, and there is no time limit on when you need to consume frozen Perpetuem or Sustained Energy. You may notice a small amount of crystals at or around the top of the bottle. This is due to the l-carnitine component in these two fuels, which is very hygroscopic (has an affinity for water). L-carnitine formed crystals may signal a slight reduction in potency of this amino acid; however, this crystallization effect is normal and harmless, and the product is perfectly acceptable for consumption.