Once product-market fit is achieved, the singular obsession must be retention. Before focusing on expansion metrics like NRR or efficient acquisition (CAC), you must first prove you can stop the "leaky bucket" and keep the customers you've already won.

Many founders mistakenly define Product-Market Fit by revenue (e.g., "$1M ARR"). The correct measure is the ability to predictably create customer value. This is best quantified by a leading indicator for long-term retention, not sales figures, as revenue can be achieved without true market fit.

The key indicator of a healthy freemium model isn't the specific retention percentage but whether the curve flattens over time. A curve that continuously drops to zero means you are not building a sustainable user base and are simply starting over with each new cohort of users.

The true indicator of Product-Market Fit isn't how fast you can sign up new users, but how effectively you can retain them. High growth with high churn is a false signal that leads to a plateau, not compounding growth.

True, scalable SaaS growth isn't just an upward line of new user acquisition. It's achieved when the user churn curve flattens out, indicating a core group of users who are activated and never leave. This creates a stable, compounding base upon which new acquisition efforts can build.

Hux's founder measures success not just by retention, but by the passion of retained users. When users start writing in daily, angrily demanding bug fixes, it's a strong positive signal. It means the product has become so essential to their routine that they care deeply about its improvement.

The ultimate proof of product-market fit isn't just low churn; it's a "smile curve" on a cohort retention chart. This occurs when users who previously canceled later return to the product. This "just kidding, I'm back" behavior is a powerful signal that the product is indispensable.

Product-Market Fit isn't just any hockey-stick growth. The founder of Jeeves defines it as the moment your target customers—the ones you want to grow with long-term—start coming to you organically. Early growth from non-ideal customers can be a false positive.

The unambiguous signal of Product-Market Fit (PMF) isn't a magic number in your analytics. It's when customer pull becomes so strong that it breaks your supply chain, logistics, and team capacity, forcing uncontrollable growth even without marketing spend.