all valid points. from my experience, it's important to perform a cohort analysis alongside the cLTV analysis. these complement each other and bring in more insights and clarity as to what's going on in your business and how well your churn/expansion assumptions held in the past.
Jason Cohen from A Smart Bear also has a lot of interesting insights on the LTV calculation and use. For example:
http://blog.asmartbear.com/why-i-dont-like-the-ltv-metric.ht...