I've just harvested yeast out of a primary that had brew sitting on it for 5 weeks. Stuff looks great. Plus, I now have enough yeast for several more batches. :rockin:
I also have yeast in the fridge from earlier washings. I'm slowly going through those too. I typically have the brew on the yeast for at least a month. No issues using washed yeast so far... It also gives you more flexibility, IMO, since you don't need to worry about the store having your yeast in stock, or not... Once the yeast is ~4 weeks old I make a starter to ensure it's fully ready to rock and roll. Had great results so far, even using yeast that's 3 months old.
I would suggest labeling the jars with what strain is in them, when it was harvested/washed, and which generation it is, or was from... Such as the batch I washed last night... I put the strain, yesterdays date for harvested, and "1" since it's the first harvest of that strain. I don't think I'll harvest the yeast from the first brew, but could with the third or fourth batch... It will give me more time to use the same strain without having to buy it again...
Personally, I'm doing this with strains that I can see using in future batches, or more often. So far, I've washed Wyeast 1728, 1084 and now 1335... Covers the majority of what I'm brewing right there.
