Refreshing by using the keys doesn't mean you'll get the discount with the ninjas that you want. There have been many times where I got certain ninja such as iruka, sailor, minato at 30% a lot in one week (happened to me last month) and in one week having a ninja showing up less frequent. Note: I rarely buy keys. What you should be doing is spend on keys by the end of the week (wednesday) since you get 5 free keys each day and you might get a discount through them.