Expected Lifetime: Churn Formula vs. Experience Data
The average lifetime is calculated simply by using the geometric distribution's mean formula. If probability of churn in any month (or simply percent churned in a month) is 0.2, then the expected life time of a customer is 1/0.2 = 5 months.
Here you are filtering the unchurned customer at the first step (filter(Cancelled == &quot;TRUE&quot;)) and therefore you get the average lifetime of the churned customers in your sample rather than the average lifetime of any customer.