The Retention Signal: Why Behaviour Change Is the Only True PMF Indicator

The retention curve that flattens rather than declining to zero is the right visual for PMF. But most founders applying this framework miss the crucial question underneath it: are users returning because they remember to, or because their workflow now breaks without it? The difference between habit-retention and structural-retention is the difference between polite loyalty and actual PMF. Habit-retention dissolves when a competitor offers a discount. Structural-retention survives a price increase because removing the product breaks something important. There's a blunt test worth running: what happens in your customer's workflow when your product is down for 48 hours? How they respond tells you more about your PMF than six months of satisfaction surveys.