“Revisit your assumption every now and then — every 6 months or whatever — or at least control that gap between what we're sending and what is actually happening is not too big.”

Revisit signal engineering assumptions every 6 months — they drift as your business changes

Signal engineering is not a set-and-forget system. Pricing changes, monetisation experiments, new channels, and macroeconomic shifts all alter which users are actually valuable — meaning the engineered values sent to ad platforms gradually diverge from reality. Thomas Petit monitors the gap between predicted and actual value; when it widens beyond acceptable tolerances (especially at the country level), he updates the model rather than letting the platform optimise against stale assumptions.