A Work Group commits to resolve and deliver Implied Requirements in the most timely and satisfactory way they can find. They are not committed to specific dates. But they do have an obligation to make their efforts visible through what becomes the ultimate trouble signal, low Completion Headroom. Headroom disappears when developmental activities fail to match those of Comparable Work. A common problem is the well-meaning escalation of requirements by people too close to a problem.
Therefore: Divide a task into an urgent and deferred component such that no more than half of the developmental work is in the urgent half. Defer more if required to acquire sufficient Completion Headroom. Defer analysis and design of parts that won't be implemented.
This advise runs counter to conventional wisdom. Often a split is just a way to get back to the basic work that had been originally planned. Trust Architectural Substitution to cover for omissions and inconveniences caused by incomplete "up-front" work. Both halves of the split will appear in the Work Queue with distinctly different urgency.