[paulmatthijs]

It totally depends on your business model. Is your expected ARPU 10, 100 or maybe 1M?

I'd personally focus on a KPI that tells you something about how much your customers like your product, and can't live without it. Aim for turning even a few of them into evangelists. Retention is the main force driving that.

But once you get that deep, it's just as easy to implement a full AARRR funnel that will give you much more insight.