You will no doubt find others particular to your business. Repeat rate is a strong indicator of future activity. While you've got your hands dirty down there looking at customer segments and repeat rates, it might be a good time to also take a look at customer Recency. The repeat rate is a Frequency idea, the 2nd most powerful predictor of future behavior, but one of the easiest to track and measure. If you want to be able to predict the future actions and value of customers even more accurately, you should also track Recency, the number of days or weeks since a customer last engaged in a behavior.
Recency is the number one most powerful predictor of future behavior.
The more recently a customer has done something, the more likely they are to do it again. Recency is why you receive another catalog from the same company shortly after you make your first purchase from them. Recency is the most powerful predictor of future behavior. Think about it this way. Repeaters who haven't repeated Recently are former best customers.