So before I get into my question, let me explain what I do and why I do it, which should help eliminate all the "well, why don't you just brew up 5 gallons and be done with it" statements. OK? OK.
Time is a precious commodity, and I don't get much of it with two little kids under three. So I've moved from doing five-gallon all-grain brew days to smaller two-gallon all-grain brews in the kitchen on the stove top. They're easy, low maintenance, no stuck mashes to draw out my brew day, it takes less time to come up to boil, and clean-up is faster, too. With a two-gallon all-grain brew day, I can usually get it done in less than four hours (from start to finish) and still have the flexibility to walk away from things and take care of the kids — not so much with a five-gallon mash/lauter system. It's easier to carve out a little time for smaller batches than attempting a larger batch and having something go wrong and take up an hour or two of time that I just don't have.
So in short, I'm able to do two-gallon batches with ease and still allows me the flexibility to brew all-grain while being short on time. (With the added benefit that I can also do a variety of beers and test out new recipes and have a wide array of home brew on tap or in bottles.)MY QUESTION...
I've read about how some craft breweries brew multiple batches over time and just add it to their large fermentation chambers over a period of a few days. Could I take the same principle and apply it to the home brew scale? In other words, lets say I brewed up batch one (2.5 gallons) on a Tuesday and began fermentation that night (in a 5 or 6 gallon carboy), could I brew up the same batch again (2.5 gallons) on a Wednesday or Thursday and essentially add it to Tuesday's batch to double it? Is there an ideal time (if any) to add to the fermenting batch and a cut-off time where it just wouldn't be smart to do so?