What did we learn about machine learning?

This is part 2 in a series about Estimating the LTV of new SaaS customers. To do this we're taking all the datapoints we have about a user after X days and seeing whether we can predict how much revenue they'll spend in their first year.

In Early Prediction of Lifetime Value (LTV) we left off when we had a CSV full of features and the Year1Revenue(Y1R) that we were trying to predict. It was time to put the pedal down and see whether machine learning is all it's cracked up to be.

It begins: The promotion 

You’re a SaaS business. You've been acquiring customers and on average they're worth about X. Somebody clever suggests a promotion, "$5off your first order".