I don't know which recipes you are using for the breads, but some of the longer-sitting ones (baguettes, no-knead, etc) use only a quarter teaspoon yeast per, say, every 3-4 cups of flour. If you are looking to extend your supply, that is.

I keep my starter in a small jam jar or screw-top tupperware, since I only keep about a quarter cup from day to day (add in a quarter cup water, mix well, dump half or put into levain, add 2 tablespoons flour to remainder). And if you are baking daily, it can stay on the counter since you'll be feeding it.

Yay for sushi!