The planning horizon is the amount of time an organization will look into the future when preparing a strategic plan. Many commercial companies use a five-year planning horizon, but other organizations such as the Forestry Commission in the UK have to use a much longer planning horizon to form effective plans.
In manufacturing, a planning horizon is a future time period, during which, departments that support production will plan production work and determine material requirements.
In Economics, a planning horizon is the length of time an individual plans ahead. It's important in the quest for total value, as opposed to short term pleasure consumption.