Yeast culture method?

Instead of yeast washing after primary fermentation in a carboy, how about this?

I usually make a 2l starter in a 4l flask. Then I chill overnight, decant the liquid and pitch the slurry.

What if I make a 3l starter and prior to chilling, pour a quart of the well-mixed (stirplate) starter into a sterilized mason jar and put that in the fridge. The remaining starter is chilled, decanted, and pitched like usual. The mason jar can be pitched (after decanting) into my next 3l starter.

Now I don't have to wash the yeast or collect it from a carboy.

This is how I culture my yeast bank. Everytime I make a starter, I take about 8- 15mL vials of yeast slurry and mix it with an freeze protection liquid. This helps preserve the yeast, and it's better than washing.

I think that would work fine.

But one of the reasons for pitching from the slurry of a fermented batch it that you are selecting for the best yeast for your beer/process/water. So you would lose this benefit If you do it the way you are suggesting, you would be selecting for the yeast that does best in your starter not the beer. But if you have a yeast that is working really well for you you can do this to maintain that yeast.

I think a lot of breweries have yeast banks at places like white lab, that they have grow up big slurries that are periodically shipped to them, but for day to day use they are pulling yeast off their fermenters.

Yep this works fine as long as you can re-pitch within a month or so. If it goes longer you should wash the yeast before pitching it into a starter so you don't end up with autolyzed yeast in your brew. I would use this method if I didn't use so many freakin' different yeast strains...

Doing what you are suggesting, the yeast growth that occurs with each subsequent re-pitch is less than re-pitching yeast, and presumably sanitiation is tighter as well since you only have a flask and not your whole end to end brew system to contaminate the yeast. This allows you to count each subsequent starter re-pitch as 1/2 generation rather than a full generation when considering how long to keep re-using the yeast.