Preparation of new assessment list.

It shall be in the discretion of the Commissioner to prepare for the whole or any part of the Corporation a new assessment list every year or to adopt the valuation and assessment contained in the list for any year with such alterations as may in particular cases be deemed necessary, as the valuation and assessment for the year, giving to persons affected by such alterations the same notice of the valuation and assessment as if a new assessment list had been prepared : Provided that the valuation and assessment contained in the list for any year shall not be adopted for a period exceeding five years.