The term of the Mayor (Class I) shall correspond with his official tenure, or, if the member is the Mayor's designee in the absence of the Mayor, the designee shall serve at the pleasure of the Mayor during the Mayor's official tenure. The terms of the members composing Class II and Class III shall be for one year or shall terminate at the completion of their respective terms of office, whichever occurs first. The term of a Class IV member who is also a member of the Zoning Board of Adjustment or the Board of Education shall terminate whenever he is no longer a member of such other body or at the completion of his Class IV term, whichever occurs first. The terms of all Class IV members first appointed pursuant to this chapter shall be so determined that, to the greatest practicable extent, the expiration of such term shall be evenly distributed over the first four years after their appointment as determined by resolution of the governing body; provided, however, that no term of any member shall exceed four years and further provided that nothing herein shall affect the term of any present member of the Planning Board, all of whom shall continue in office until the completion of the term for which they were appointed. Thereafter all Class IV members shall be appointed for terms of four years except as otherwise herein provided. All terms shall run from January 1 of the year in which the appointment was made.