Well Racky, this may not be scientific but I hope to keep being fed right up until they pull the plug. 😛
Then again, I only grow in soil, so the only way to ‘stop’ my girls from feeding is to pull them. As for hydro growing, some of the best studies I’ve read suggested that in a blind taste test between flower that was ‘flushed’ and flower that was fed until harvest showed “no stastical differance”, in other words, stoners couldn’t tell any differance.
Hope that helps.