You can get away with breaking all of the other rules at least once in a while, but you can't get away with breaking this one. Readers will accept almost anything from you if you don't make them feel they have wasted their time and money. Remember, you can bore readers in a lot of different ways. It doesn't necessarily take a dearth of action; too much action can get you the same result. Everything in writing, like in life, requires balance.