It is, a little. You can't sustain a listening rate of less than nine books per year. That's because there are no plans that provide less than one credit per month, and you can only put your account on hold three months per year. I suppose you could bank extra credits indefinitely, but if you only want to read six books per year, then after two years you will have a year's worth of credits banked. After four years, you'll have two years worth of credits banked.