I've been bottling my kombucha in big batches, much like I do beer, and storing it away for the winter months when the scoby doesn't produce as quickly. Some of these bottles have been around now for as long as 5 months. When I crack now the brew is something akin to beer or champagne. Bubbly, not the least bit sweet, but not vinegary, either.

I've never tried water kefir. I made a couple batches of milk kefir and found that the result wasn't worth the time and effort I was putting into it.