I emailed Imperial about A24 a few months ago and they said that the addition of Conan would eliminate the "false terminal". I dont really understand how it can prevent the A20 side from slowly breaking things down, but maybe the conan being there just consumes the available sugar faster than the A20 would? Anyway their whole response is below. I had also asked a question about over building starters, also covered below.I personally get about 5% more attenuation out of A24 than 1318 (under similar grist/mash conditions).
Do we know how active the STA1 gene is in the Sacc trois strain? @suregork have you tested that strain?
For the most part, A04 Barbarian is adding to the overall ester profile of A24 - lots of stone fruit esters, peaches and nectarines and such. The FG is going to be fairly similar for both the A04 and A20, however, with the addition of the A04 in the blend, fermentations are a bit faster. A20 likes to hit a false terminal and then slowly finish out fermentations, with the blend this does not happen. The A04 is slightly more flocculent, so the straight A20 will be hazier than A04 and the A24 will be right in between in terms of haze- make sense?
Propagating blends can be a little tricky, especially when you are working with sacch and brett blends. When working with just sacch blends, it's far easier to get close to the original ratios. I see no issues with making a large starter with a single pouch of A24 and reserving some for future brews. However, if you are harvesting and re-pitching the A24, you'll absolutely run into some alteration of the original 50/50 blend. Considering that the A04 is more flocculent, over time, especially between gen one and gen two, you will see A04 Barbarian become the more dominate strain.
Personally, I really like the A24. I think it provides some nice esters that are really hard to get when just using the single strain of A04 or A20. And, because you are not packaging this beer for market, slight differences batch to batch is not a terrible thing.