The amount of feeding depends on many different factor.
The age of the fish: younger fish need food more often
The amount you feed: it has been argued small amounts of food more often, are better than larger amounts all at once
The type of fish: large predators may only need to be fed once every 3 or 4 days
Preference of the keeper: In the wild, most fish don't feed every day, and therefore, the hobbyist has a bid of leeway on feeding. Some people prefer to feed once a day everyday, some prefer to feed twice a day with one day a week of fasting. I prefer the latter, it's really up to you how often you feed, as long as the fish eat all of the food in 30-45 seconds, and none of them are either really fat, or really skinny (barring a pregnant or eggy female).