Update - I actually didn't have a problem at all. Well, I had a different problem. I added a little less than 1/8 tsp. to each 2-liter bottle. after a week, I had very little to no carbonation. So I added about another 1/8 tsp. and then the bottles firmed up nicely. And then the yeast pooped out on me again. fortunately, they quit with just the right amount of carbonation this time! So you can get lucky by adding just
the right amount of yeast and then no need to refridgerate!
I wouldn't actually recommend this though. I could probably do this 100 more times and I'd probably end up with flat or exploded bottles each time. It was easy enough to mix up just a few at a time with a funnel, so that's what I'll be doing in the future instead of making all 8 2-liters at once.