Generate a 500-word article outlining a comprehensive retention metric framework for SaaS businesses.  The framework should cover key metrics beyond simple churn rate, encompassing user engagement, feature adoption, and customer lifetime value (CLTV).  Include explanations of each metric, how to calculate them, and their significance in understanding customer retention.  Discuss the importance of setting benchmarks, tracking progress, and using the data to inform retention strategies.  The article should also address how different metrics can be combined to create a holistic view of customer retention.  Finally, provide examples of how SaaS companies can use this framework to improve their retention efforts and increase CLTV.  The article should be written for a business audience familiar with basic SaaS concepts but not necessarily experts in retention metrics.  The framework should be adaptable to different SaaS business models and scales.