(1)When the table of revenue-rates for any area has been finally published, the rates specified therein shall remain in force for a period of thirty years.
(2)Notwithstanding anything contained in sub-section (1),—
(a)revenue-rates may be altered or revised in any year after the expiry of every ten years from the date on which the table of revenue-rates was introduced, in such manner and to such extent as may be prescribed;
(b)when the circumstances of a local area are such that a fresh determination of the revenue-rates is in the opinion of the Administrator inexpedient, he may extend the term of settlement by such further period as he may think necessary.