On initial roll-out...done three now...I reach a point in the delivery roadmap where specific stakeholders/partners/allies are brought into the mix to perform a "validation" of the numbers, designs, etc planned for production usage.
For each milestone reached in the roadmap, another round of validation exercises are executed with relevant stakeholders/partners/etc and specific steps/outcomes listed out for those validation exercises.
Beyond the roadmap delivery, recurring "operational" validation exercises are identified in such a way as to register those parties involved/accountable (think RACI), frequency, and escalation points. The collection of which acts as a barometer to determine if a push to production usage reaches sufficient approval level or needs to be delayed. I say "sufficient" because there are times certain data sets, reports, etc may not get a full approval/validation, but it's agreed that no response can be regarded as a non-specific approval whereas the period of time solicited for such acts more as an opportunity to object to a production push.