S. Cerv, While I agree that it's likely that most of us don't handle our yeast with enough care, are you saying that yeast don't produce off flavors of fusels, increased esters, phenols, etc at temps in the 70's? and every time that happens it's because of a minor contamination issue? That would be very surprising to me.
the missing piece is the maximum cell density S. Cerv mentioned. 3L would be about 600b cells, if you pitch those into another 3L you will end up with about 600b slightly older, less vigorous cells.