Better rule: protect the important outcome, not the original date of every task.
Keep one source of truth
When plans change, people often create a new list to reflect the new reality. Soon there are several versions of the week and no confidence in any of them. Keep one board and move the task in place.
Separate urgent from merely new
A new request is not automatically more important than work already promised. Put it on the board, then decide what it displaces. A visible week makes that trade-off harder to ignore.
Use movement as information
If the same task moves three times, the problem may be unclear scope, a missing decision or an unrealistic estimate. Rescheduling is not failure; repeated rescheduling is a useful signal.
Cadence keeps that signal visible with a simple drag. See the realistic-week guide or the feature overview.