Question
I know with my "best" and "average" customer LTV that my current cost per acquisition (CPA) is good.
However, if I was just looking at my "worst" customer LTV the current amount I'm paying in CPA is way over.
How do I judge what I should be spending on advertising based on these 3 LTV segments (best, average, worst) I have for my customers?
Answer
In my experience the easiest way is to change what you're optimizing towards, at present your CPA appears to be that best/average/worst are all equal to 1. Why not change out your acquisition model to optimize towards the LTV you've defined.