Upon further reflection, my answer for the exam would be short term horion. The reason is that it is stated in the text that pieces of future liability attributable to service, salary, and non-market risk such as demographic risks and plan changes are not factored into the asset-liability framework. The text concentrates on accrued benefits and retirees. In practice, one could hedge away future liabiliy attributable to mortality risk etc. But lets just focus on passing the darn thing.
for the exam, lets just stick to the cfai answer… example - reading 21, question 1… the book clearly states… “although going concern pension plans usually have a long time horizon, the XYZ plan has a short time horizon because of plan demographics”
Clear