A response to your question depends on whether applicable FAR clauses are included in the contract. If so, please refer to the applicable FAR clause on ordering which addresses the period of performance for issuing orders. The ordering clause at FAR 52.216-18 Ordering states:
52.216-18 – Ordering.
As prescribed in 16.506(a), insert the following clause:
Ordering (Oct 1995)
(a) Any supplies and services to be furnished under this contract shall be ordered by issuance of delivery orders or task orders by the individuals or activities designated in the Schedule. Such orders may be issued from __________ through ____________ [insert dates].
(b) All delivery orders or task orders are subject to the terms and conditions of this contract. In the event of conflict between a delivery order or task order and this contract, the contract shall control.
(c) If mailed, a delivery order or task order is considered “issued” when the Government deposits the order in the mail. Orders may be issued orally, by facsimile, or by electronic commerce methods only if authorized in the Schedule.
In addition, the Indefinite Quantity clause (FAR 52.216-22) provides for the insertion of a date in paragraph d, after which no "deliveries" are to be made. When this clause is used for services, this is presumably the final date that services may be performed.
52.216-22 -- Indefinite Quantity
As prescribed in 16.506(e), insert the following clause:
Indefinite Quantity (Oct 1995)
(d) Any order issued during the effective period of this contract and not completed within that period shall be completed by the Contractor within the time specified in the order. The contract shall govern the Contractor's and Government's rights and obligations with respect to that order to the same extent as if the order were completed during the contract's effective period; provided, that the Contractor shall not be required to make any deliveries under this contract after ___________[insert date].