I have 2 going at the moment. One is straight Wyeast Lambic Blend, and the other is my house blend from multiple sour beers that has produced some excellent sour beers.
I start fermenting with the bugs in a glass carboy, and then as the sacc fermentation is slowing down I rack some of the beer out into a 1.5 liter wine bottle, put an airlock on it and store it away at room temperature until I next want to use it. Since I have two primary mixes I'm using and brew about every 4 months, each gets 8 months between use to increase their colonies of bugs.
This maintains the original bug mix. After I've taken my sample, I'll often add dregs of other sours to the main beer, so each one usually ends up different.