Within the repeat settings of your work item you have the option to have your tasks created from one day before the work start date to one year before the work start date.
The default is that tasks are created 2 weeks before the work start date. When choosing the creation date for the tasks within the work item, we recommend that you consider how far in advance you will need the tasks and how likely it is that something will change on a task level. The reason being that if you change something in the work template, the changes will not carry through to work items, where tasks have already been created and you will then have to reset them manually.
Keep in mind that the task creation option is dependent on how far out the work is set to create, meaning you cannot have tasks created before the work item is created.