Thanks for the replies.
On average, I brew every three weeks.
I alternate between WLP001 and WLP002 (occaisionally 005 or 007).
I’ve been filling a quart Mason jar after the initial ferment and then six weeks later using a portion of the jar.
I guess I’ll start saving some slurry from the second and third ferment as well.
Assuming good sanitation, I wonder how long it would be before there was a negative effect from mutation?
It depends on the strain and gravity of the beer and how well you aerate… nutrients… etc. I feel comfortable ~3 generations but not so much because of mutation, rather I feel less comfortable about the sanitation of the strain after that (either that or I am at a high gravity and I don’t repitch from much higher than 1.070.)
FWIW, I only get new yeast about twice a year (unless its a strain specific to the beer I’m making) I save from 1st and second pitches (which is actually 2nd and 3rd since i get brewpub yeast a lot) and then branch off of those to 4 generations, regrowing if I have to b/c its been too long.
so point is, you can go a good long while if you keep good sanitation practice and brew often enough to keep the yeast healthy.
Mutation takes quite a long time, AFAIK. Sanitation is the real concern.
back in the 90’s i was doing 10 gal. each week. on friday i’d rack, and saturday the new beer went right in on top of the dregs. great for a couple months - then i noticed the beers were coming out more bitter than calculated. freaked me out. (all i make is ipa’s). then, got working for the railroad, no schedule, on call 24/7 and what little time i have is precious - brewing was on the back burner. couple years ago, things changed and i had some time to get back brewing and i also got one of these here fancy computers. things changed in the homebrew world since my setback. these forums saved my sanity when i saw a post about rinsing/washing yeast. apparently my sanitation is o.k. because i’ll run a yeast for 20 or 30 repitches or until i get the urge to change with no problems. time is the concern. i don’t know when i’ll be able to have some time to brew let alone make a starter, so having a couple mason jars filled with ‘ready-to-go’ yeast was a real blessing. sure, it’ll get a little bitter after 10 or so batches of ipa but most of the time i’ll brew a ‘sissy beer’ to give to my sissy beer drinking friends and when i harvest THAT yeast, it’s like having a new/clean pitch. i guess it all depends on your situation.
Yeah, I really like having a jar or two of slurry in the 'fridge for those times when I find I can brew on short notice and don’t have time to make a starter.
Of course, I keep a couple of packs of dry yeast around for the same reason. Gotta have a plan B!