Nothing wrong with your thinking there. I do that myself. I try to get yeast well in advance of when I need it. I make a big starter, chill it, decant it, and put it into several small mason jars. When I want to brew I use one of these mason jars to make a starter. You can also use the cake or yeast wash on the back end.
As far as never buying yeast again, yeast does get old, and washing does eventually lead to over contamination and mutation. The only way to stretch yeast over a year or more is to innoculate slants to create a yeast bank that can be stored in the freezer. That is a bit more work, and still some has limits on length of storage.
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