How often should cats be fed?

I only feed my cats dry food, and we have an 'open bowl' but since my cats are Persians, and very picky, the will only eat the food for the first 3 minutes after it is put in the bowl, the rest is considered "old" and won't be eaten. I asked my cats how often they feel a cat should be fed, and the answer was unanimous. ANY time they are asked to be served fresh food.

Seriously, if they are that hungry and dry food is out, and if they only eat a bit of it if you open a new can, I'd say you are feeding them plenty.