You want to have several plan dates calculated in a maintenance plan.

To have several plan dates calculated in a maintenance plan, you use the scheduling period parameter. The scheduling period defines the time interval for which the system calculates the planned dates for the maintenance plan. For example, if you enter 12 months as the scheduling period, the system calculates the planned dates for the next 12 months from the current date. You can also specify the end date for scheduling, which is the last date for which the system calculates the planned dates. The scheduling indicator determines how the system calculates the planned dates based on the cycle, the shift factor, and the tolerance. The call horizon defines the percentage of the cycle that must be expired before the system generates a call object (such as a maintenance order or notification) for the planned date.

References: 1: Scheduling Maintenance Plans - SAP Learning 2: Maintenance Plan Scheduling Parameters - SAP Online Help