Is any FG other than 1.000 an acceptable (ie fully attenuated) FG from a beer which has been fermented using an appropriate amount of brettanomyces and or lactobacillus? If so, how do you really know when the attenuation is done? It's a bit more complex than the "check for three days straight" rule. Perhaps there are published acceptable attenuation ranges for strains of brett that I haven't been able to find.
I am not sure if there is any published work on it. I have heard @OldSock state to check it over a few weeks to months to see if it is still moving. I checked my Lambic at 17 months and it was at 1.006. At 20 it was down to 1.001. Other bacteria play a roll as well, with Pedio and Brett working in tandem it should go farther faster. I have a 100% Brett L fermented Oud Bruin that was at 1.011 after a month of primary, and 1.008 a few months ago, and is down to 1.002 now at 14 months.
The FG's gonna be in play; drink it/bottle it when you're where you wanna be with the beer. If you want to age it, bottle at a lower FG, if you plan on drinkin' fresh, higher is okay.
I guess my point is this: my intention for these beers is certainly not to drink them all fresh - to see how they progress as they age - and I'd like to know they're done before I put them in bottles. @jbakajust1's point is a good one - just give it time, closer to 1.000 the better.
There are sour beers that finish anywhere from sub-1.000 to 1.020. Depends on the wort and the microbes, no real way to project a range. Waiting for the gravity to be stable month-over-month is the only way to be sure.
I threw my brett saison intoo bottles when it. Reached 1.002. What's 2 gravity points going to do over time? It turns out that if you brewed an excellent beer, you won't have them in the bottle long enough for bottle bombss!
