There are certain things we need in life that must be bought and replenished time after time - toothpaste, guitar strings, food (a personal shopping list of mine). Food goes off. Eventually it starts to grow mould and becomes stale with a disposable future. Information is the same - leave it long enough and it becomes outdated and you need to get a fresh replacement. In a book store, the paper becomes encrusted with yesterday's news, but online authors are keeping up with their niche and its cha.