This is a graph I create for my client base when they request a File Power project. I measure future sales as a function of time since acquisition.
The relationship (in this case) looks nearly linear - it is not, but it is one where the customer keeps spending money year-after-year.
Here's the relationship, summarized in tabular form.
Tomorrow we'll extend the table to profit. This company is a good one - there is sufficient downstream profit to grow this business via customer acquisition.
You likely produce this table for your company. The table (and the one I'll share tomorrow) form the basis for your investment strategy.