I understand that I can use this constraint in MS Project, but really, what is a good use case for this? When does this constraint make sense?
This constraint makes sense when you have a task with any of the following characteristics:
- It can take place at any point in time, up to a point, but there is a future event/date/task by which it must be done
- There are higher priority tasks which you would prefer take place before said task, but which are not literal predecessors of the task
- There is an external reason why it makes sense to leave the task as late as possible (such as that outlined by mwan)
As an example, I commonly use it for all pre-deployment preparation tasks. The actual deployment date/weekend/milestone/task happens at a time driven by the bulk of the project plan, but the tasks to prepare the environment, complete the service transition documentation etc. can happen at any time prior to the deployment; but clearly you want them just before deployment. There is no point preparing the service transition documentation at the beginning of the project, you want it right at the end just before actual deployment.
So the backloaded tasks becomes a pre-requisite for the deployment milestone/task using As Late As Possible, which means they butt up against the deployment tasks and don't get scheduled earlier in the project.