Making and keeping a sourdough starter is both a pain-in-the-ass and highly rewarding…if you can remember to feed it, that is.
My starter is pretty young but I feed it often and leave it on the counter every few days to let it really ferment and grow more sour. Generally, I replace one cup of starter for one tablespoon of packaged yeast in just about any recipe. The rise time is much longer than with a yeast dough but the flavor is worth every hour. The first proof for this loaf was about 12 hours. The second rise (in the loaf pan) only took four hours. I wait until the dough is about two inches over the top of the pan before I bake. Some days that is only a couple of hours. It really depends on the weather and the energy level of your starter.