To me, just make sure their stomachs dont become shrunken in and they look in general good health. If that means 20x a day the. Thats what we should do. I personally feed once a day and sometimes twice a day when i am home. I also skip sundays.
Long as your fish arent starving and wasting away, do it your way.
You also have to look at it in terms of water quality. More food, more waste, more algae. Its a balancing act. I generally feed my fish as much as my system will reasonably allow.