Something I have been doing for a while, espeially since I have never really bothered with starters, has been to brew batches one week apart and simply rack one beer out of the primary and pour the next batch directly into that same fermentor onto the yeast cake. Lately I have been always starting a Festa Brew wart kit the week before I brew all grain just for this purpose.
Though the results have worked out just fine, and it saves me some minor hastles, I know there have to be some theoretical downsides. I’m not washing the yeast etc. What would be the reasons against doing this? How would doing something else improve my beer?
I find the yeast a little cleaner when using Festa Brew than a fresh batch of all grain containing much more trub.
Also, since at least one batch had been taken over by a wild yeast without me noticing, my second brew on that yeast was also tainted (obviously). Since then I tend to stick my head right in there and give it the old smell test. Since then I have only detected a wild yeast once and did not reuse the cake.
Like I said before, I actually get really good results from this.