I'm not sure why but there is no metric showing the average length of a subscription i.e. how long a subscriber stays subscribed on average, ideally in days. This is needed to make important projection decisions such as how much you can afford to spend on ads (based on how long you project the customer will stay), figuring when customers are likely to experience product fatigue so you can reach out to them and reduce churn, as well as informing decisions around how to increase your customer lifetime value. Could you please include it as a core metric.