Scrum says: time-box & prioritize items to maximize value. In the release planning meeting, in the sprint planning meeting, at the stand-up meeting, every day during the sprint
Startup and Open source lessons and Agile Software Development suggest: release early, release often, and listen to your customers
eXtreme Programming principles: Baby Steps (to reduce risks and get early frequent feedback) and Improvements (don't wait for perfection,don't leave behind you a mess)
Complexity Science suggests: strive for safe-fail experiments whose success can be highly valuable and whose failure can be very informative
Lean software development principles: Amplify Learning (with rapid try-it, test-it, fix-it feedback ...