“Retention is the ultimate proof of value. If a user comes back you're creating something real. If they don't, nothing else matters. Revenue revenue revenue — but retention really is the only way to have lasting value and the only kind of real moat.”

Retention is the only real moat — if users come back, you're creating something real; if they don't, nothing else matters

Schlenker positions retention not as one metric among many but as the single indicator that validates everything else. Opal reached day-1 to day-7 retention on par with or better than Duolingo, Spotify, and Strava. His argument: it is relatively easy to convince someone to try and pay for a product; retaining them over months and years is the hard part that compounds into a durable business. High early retention is also the prerequisite for the cohort stacking that makes subscription economics work over years.