2 liter soda bottles

using 16 0z. plastic, and its working well. are 2 liters a good option?

Think of the 2L as bottling a pitcher. If you have the occasion to serve (or drink yourself) a pitcher, then go for it. They are great to take to parties - you don't have to worry about gathering up your empties. BTW, I have kept one open til the next day, it just looses a little carbonation, but not bad. I prefer 16-20oz and 1L, particularly the wide mouth 1L bottles, not the standard skinny cap ones.

how long before its flat?