What are the best tools to use for app subscription LTV calculations? (eg. Chartmogul versus alternatives)

I can share the approach we use to calculate subscription LTV:

Lifetime

We calculate a max lifetime for each cohort:

1. For cohorts with 2-5 renewal events, project the rest of the profile based on historical averages by subscription and country, to project maximum lifetime.
2. For cohorts with 6+, use the actual retention profile and fit curve to project maximum lifetime.

Value

Use avg. subscription price, weighted by duration and country, but normalized to a daily value.

LTV = Lifetime(days) * Value(daily)

A limitation related to one of your other threads is around treatment of annual subscriptions, oftern with no renewal data, for newer apps or newly launched annual plans. I'm curious how others are treating this.