At a hotel, the time taken between when a customer makes a reservation and their actual arrival is called the Lead Time. Sometimes this time period has to be restricted.
Because it can help with the management of room availability overall, ensuring that profitability is always maximised. This usually applies to an offer, which is available up to a certain number of days prior to arrival. Can be combined with other restrictions. For example a 15% discount, which is non-refundable, up till 30 days prior to arrival. Such promotion are set-up not to coincide with the regular booking window, in order not to down trade ADR on your normal demand.
You could think of a Lead Time Restriction as a kind of insurance policy! The Restriction requires an individual customer or group to meet or exceed a specified advance notice in order to complete the reservation.