There several types of planning to deal with. This website is trying to give you some insight in the services I can give.
EPC network planning were Engineering, Procurement, Construction and Commissioning are connected in a integrated planning. Timing, progress and critical project durations will be exposed for the right decisions can be made by the management.
Maintenance Planning: In a a maintenance environment all maintenance routines will be planned in time with the hours and durations to ensure integrity. This is a different type of planning, but the output can be the same in a planning Gantt chart.
Long Term Planning: There are different types of time frames for businesses to work with. The leader board wants to look-up 5 or 10 years upfront for investment and decision making . Where Construction management wants to look -up very short term till medium term.
Planning is the ideal world that does not exist.
To meet the real world there are several methods taking in account the disturbances, project bandwidth. One method is to make a risk assessment of the planned work where all the high level planned items are put in a planning model to analyze it with the right people, like construction leads, managers etc and of course the vendors to investigate the likely hood will happen to achieve a activity in duration and work. The outcome will be a steer to for the project duration.