IMO here is some of the best info on Mr. Malty.
Quote:
Wyeast says starters reach their maximum cell density within 12-18 hours, which sounds about right to me. Some sources suggest that maximum cell densities are not achieved until 24 hours and others as much as 36, but the return on waiting that long is minimal. Let's just say that the bulk of the yeast growth is done by 12-18 hours. I like to pitch starters while they're still very active and as soon as the bulk of reproduction is finished, usually within 8 to 18 hours. This is really convenient, because I can make a starter the morning of the brew day or the night before the brew day and it is ready to go by the time the batch of wort is ready. There is no need to make a starter a week in advance, because I pitch the whole starter, liquid and all (up to a certain size of starter). Yes, you can wait longer and completely ferment it out so you don't have to pitch the liquid, but if you're going to do that, you should use a larger starter and allow the fermentation to go complete cycle over several days, chill, decant the beer and pitch just the yeast. If you're making a smaller starter, it is better to just pitch the entire active starter within about 6 to 12 hours of pitching the yeast into the starter.
