Forgive my ignorance, as I am just starting out. When I take my established starter out of the fridge after being in there a week, do I discard some before feeding, or just feed it if I want to use it in a recipe? Also, if I leave it out after feeding but don't get a chance to use it in recipe for say 18 hours, will it be bad? In other words, can it be left out too long before using?
Lisa, you may get different answers depending on who you talk to, what type of flour you use to feed, the temperature in your house, the hydration of the starter and your feeding schedule. Some use it straight from the fridge, others refresh ( discard some then feed and allow to rise ) at least once before baking. Once it has peaked, if you left it out on the counter for 18 hours, it would not go bad, per se, but would likely have very little strength, and so you would likely want to feed it at least once before feeding.
When we first feed a starter - the yeast feast on the fresh food ( flour ) and start to reproduce. That cycle will continue, and the yeast population will continue to double each generation, until the yeast start to run out of food ( flour ) and the yeast population will start to die off. In the fridge, the cycles slow way down, so there could still be plenty of yeast ready to reproduce. I have read that once a starter has peaked and is ready to use, it can be stored in the fridge for a few days and can be used straight from the fridge, but as I said at the beginning, that can be impacted by many factors.
It depends - and more importantly - how long - combined with your taste. Longer generally means stronger - both taste and activity. Just adjust for it. Enjoy!