Any Compensation to become payable under this Act, whether by Agreement or otherwise, may, by the Agreement of the Parties, or at the Discretion of the said Justices or Vice Warden respectively, be made by the Payment of an annual or other periodical Sum, to continue payable during the Continuance of the Possession under such Entry as aforesaid, or for any less Period, and to be determinable either upon the Restoration of the Land entered upon to a State fit for Cultivation, or at any earlier Period, and may be made to cover and include as well past as continuing Damage.