I have begun washing and saving yeast as part of my regular brewing process. I'm aware that yeast, as a living organism, has a shelf life even under the best circumstances. I try to brew regularly to keep my yeast populations fresh and viable but some styles (hefes i.e.) I only brew occasionally. Does anyone make a starter for the sole purpose of settling out old dead yeast, rebuilding the population, and then re-storing the freshly propagated yeast population?