The goal should be to have less as possible tasks on the critical path.
Task on the critical path requires special attention, because a delay of such a task leads to a delay of the whole project. Delays of tasks which are not on the critical path could be acceptable, because they will not lead to a delay of the whole project. If the delay of a task not on the critical path will reach a certain level, this task (and maybe the following tasks) will become part of the critical path. Saving Changes...