I keep the fishfood (a variety of about 6 different kinds of flake and pellet) in a dry box and each tub is sealed. I had a bad experience using flake food in an automatic feeder one summer we were away. Came back and the damp from the tank must've spoiled the food in the feeder- it stank and was bad. Since then have been somewhat paranoid about the food being fresh.
I know homemade gel food is maybe best but I haven't got round to that just yet.
I also feed veggies once a week or so.