Is their stability to this mixture? What type of longevity are we talking here?
From a DIY stand point, its pretty ingenious, but from a cost comparison to the "bread and butter" DIY CO2 mixture, then its quite a leap. Your looking at almost 10 bucks a batch (if not more, once you get the yeast and juice, etc.) as opposed to the less than $1 a batch of the "bread and butter". (unless the yeast packet can be used for multiple batches which I can't tell)
So unless their is some serious long term cost savings or benefit, I am skeptical.
But none the less, still nice to see something new in the DIY world!
Well i can get wine yeast locally it cost me .79 for a foil package of dry wine yeast. Each foil pack is enough yeast to do 5 gallons so yes you can do more than one 2 liter bottle from one package. I would Divide each packet into 5.
As far as stability it is MUCH more stable. Yeast needs acid,nutrients,and Sugar to grow properly the "bread and butter mix" doesn't provide anything but sugar. I suppose you could buy a commercial acid blend and Yeast Nutrient and still use Sugar,water and yeast but IMHO juice just works better.
Longevity i cant guarantee any thing but i have had home made wine take up to 2 months to stop producing CO2 depending on the yeast used.The key here is to use a yeast that can ferment to High Alcohol volume i recommend either Wyeast Eau de Vie 21%(which is liquid only) Or Lallamand K1-V116 which can go to 20% and a good overall choice is Red Star Montrachet. I do know the two liter batchs with juice seem to last 3 to 4 weeks as apposeed to 2 but then again that could simplely be that the sugar in the juice is more complex that White table sugar and ferments slower.
The Big sell point of doing it this way is the fact that you can drink it and it will taste FAR better than the plain sugar/water DIY CO2, Just make sure that if you want to drink it that their is NO WAY any tank water can get into it, i have 2 check valves AND a gas Seperator for just that purpose lol.
As far as cost savings if you are already a Wine drinker then yes BIG TIME savings making your own over store bought. But as far as Just to provide CO2 it prolly does cost more.