I've got yeast I've been re-using for over a year. Treat it well, be sanitary, build it up in a starter and it will last much longer than a week.
Drinking a tripel brewed with yeast that was first pitched about a year and a half ago or so.
Joe Sr. How many generation is it? I had read somewhere when I first started yeast washing that more then 7 generations old could give you a different yeast aspect. Have you ever found that your strain has changed over time?