Free Credits Roll w/ Paid Credits

Been testing out F&F for a few days and needed more than just the daily cap to do some real testing, so I bought 500 credits. It was only after doing this I learned that it won’t let you roll free credits when you have paid credits. This is a little frustrating, especially as someone going from free, to dipping my toes, for the purpose of deciding if I want to shell out the (understandably, but still unpleasantly) high subscription fee.