If you are overbuilding, Id say that going three overbuilt harvests allowing you to get 4 brews from a single pouch is a success IMO. The last brew you just don't overbuild to harvest. I haven't seen/detected to my palate anyways any difference at all and the fermentations are all the same behavior. I agree with
@Dgallo in that when I harvest, after I get my mason jars sanitized and ready for harvesting, Im making sure to swirl the flask (which just left the stir plate) really well to make the starter as homogenous as possible. Not a perfect science but works well IMHO. Not sure how many generations you can do this with as Ive never tried to go past 3 harvests from overbuilt starters with A24.