I will say that based on playing around with lots of configurations, improving your retention rate appears to be much more important to long term income than sign-up rate. Relatively small changes there can have huge cumulative impacts.
For example, if you had 100 daily subscriptions and 90% retention, your equilibrium point would be around 30k subscribers. Increasing it to 95% retention would jump you to 59k subscribers. You’d need roughly double the daily sign-ups (200) to reach the same level.