What's the maximum amount of time for primary fermentation, assuming the beer is going straight to bottles next? Will it over ferment and then fail to carbonate, if left too long in a carboy?
It takes three to nine days for yeast to ferment a typical wort. After yeast consumes all the available food (or produces too much toxic alcohol) it goes into a dormant stage, flocculates and drops out of suspension. At this point it does not produce alcohol or CO2. Priming sugar is used to give the yeast a little more fuel so they will wake up and carbonate the bottle. This means that you can not over-ferment your beer.
I do not transfer my beer from primary. You can leave them for months with little flavor impact.
I've had beers in the primary bucket for as long as a 5 weeks (busy, lazy, whatever), and never had a carbonation problem in bottles or kegs, upon addition of priming sugar. There will always be live yeast hanging around. Never had real problems with off-flavors from sitting on the trub for too long either.
I don't think there are any hard-and-fast rules, but I do try to get it into the secondary in 1-2 weeks, if it's a big beer. For a regular session beer, it goes to bottling/kegging after 4-5 days anyway, as soon as fermentation is done.
I have had mine in there for 3 weeks probably max. I tend to follow the 1-2-3 rule and that's 1 in the primary - 2 in the secondary and 3 in the bottles.
The yeast don't "die" they just go dormant so when you add some fuel (ie sugar) they will get active again until they have burned that up and thus carbonate the beer.
The only real reason I even move to a secondary is out of probably an unfounded fear of off flavors from the beer sitting on all those proteins etc, but to be honest it's probably not really necessary. It's more of me just wanting to mess with it and not having the patience to leave it alone for 2-3 weeks haha.
@ Hokiesguy95: your beer was not a failure because of excess time in primary (three days by your count), that would have nothing to do with soapy, unpleasant flavors. It would take WAY longer than ten days to produce any sort of soapy flavors from yeast autolysis.
The old advice of getting the beer out of primary as quickly as possible is antiquated and need not be repeated ever again. Just because there are no visible signs of fermentation does not mean the yeast is finished working; even with absolutely zero airlock activity the yeast are still cleaning up the byproducts of fermentation (including acetaldehyde and diacetyl), and allowing proper time for this work to be done will result in a more refined beer.
My fermentation process is a 21 day primary (under controlled temperatures), and then straight into a serving keg or bottle for most beers and into a lagering vessel for any lagering or long-term aging (barleywines, etc.). This extended primary has only resulted in much better beer, not worse, and no off-flavors or undesirable yeast byproducts. Oh, and some ribbons to boot. :)
Best sanitation practices and healthy yeast let my beers sit in primary for many months. As I tend to over pitch, the extra time is not wasted by our single cell friends. Crystal clear (I stopped using secondaries some years back) and no off flavors. Sorry, I don't know how this would affect bottling as I haven't done that in over 30 years. Agree, great yeast is out there, grow it up if need be before pitching. Or just get a growler full of it from from your local micro-brewery.
I had one batch split between two carboys. One that sat on the yeast cake for only 4 weeks and the other that sat on it for 6 or 7 weeks. There was a significant difference in flavor between the two and the half that was on the yeast cake for the longer period had a strong contribution of yeast flavors and was of inferior quality to the portion that had less exposure to the yeast.
I've noticed this exact phenomenon on two different batches in this exact fashion. I will never repeat this mistake again. I will be using a secondary for anything longer than 3 weeks.
I've read where there is a risk of adding some off flavors if you let your beer sit in the primary fermenter too long. Typically when you see that there isn't any bubbling or activity for a day then consider racking to a secondary or going to the bottling bucket and add priming sugar. Or if you don't want to worry about bottle conditioning, consider kegging your beer and force CO2 into it. No worries about carbonation then.
I do not understand how people have left their beer in primary for more than 7 - 9 days. My first ever attempt was a failure because I left it in primary for 10 days. It was an Amber Ale and it ended up being very soapy tasting and unpleasant. Could possibly be the style was not meant for longer, but I would not recommend leaving in primary once fermentation has ended and one should transfer to secondary if they are going to age or condition it before bottling.
The real problem with leaving beer in primary for too long isn't the yeast, it's the hops. If you're dry-hopping, leaving the hops in the fermenter for too long can cause vegetal or grassy off-flavors. If you're not dry-hopping, then I don't think there is a problem. I've left several batches in primary for a couple of months and haven't noticed any ill effects.
I have never had a beer ferment out in 3 days or even a week, mine take typically about 2 months regardless of time of year or beer type. I am not sure if anyone else has this going on, my beers are clear once kegged and appreciated by all who drink it. When I started brewing I realised it was a patience game, I have 7 30Litre fermenters and 1 60Litre fermenter. I either brew from kits, or from tins of malt extract and boil adding 4 hop additions; 1 at beginning; 1 at 40 mins; 1 at 50 mins and 1 at 55 mins. Either way they sit in primary for a minimum of 2 months before being bottled or kegged.