Food bowls

I'm thinking of buying an automatic feeder for my cat for short absences. Now I've noticed to my amazement that many manufacturers sell outrageously overpriced silica gel dehumidifier pads that you are supposed to change every month. The reason for this is supposed to be freshness and the prevention of mould growth. If this were a problem, should the feed manufacturer also include something like this in the feed packs or am I misunderstanding? I am currently leaning towards buying one, simply leaving out the filter parts and regularly checking that everything is OK with the food. (Don't put a year's supply in there) Thanks everyone for any useful input LG