Follow up is the most common – and commonly accepted – form of checking a colleague’s reliability. In many cases, however, external factors determine whether an agreement can be fulfilled precisely. The parties to the agreement may have little to no influence on them.
The higher level agreement with the customer – whether internal or external – may have changed. This, in turn, changes all related activities down into the organization. Budgets and or resources can change, affecting what is possible. Management can alter priorities at short notice. Then there are factors unrelated to business: a colleague might become ill.
Follow up allows the agreement parties to react to change. The faster, the better.