No person summoned as a petit juror shall be required to serve more than two (2) weeks in any year in which he or she may be summoned; unless at the expiration of the period of two (2) weeks he or she shall be actually serving on a jury theretofore impaneled to try an issue then pending and undetermined, in which case he or she shall continue to serve until the trial is concluded. Notwithstanding the above provisions, if a juror has been tentatively selected to serve on a jury by the parties litigant and the juror has not been formally sworn and impaneled by the end of the two (2) week period, the trial judge, in his or her discretion, may extend the two (2) week term until the trial is concluded or until the juror is excused. Provided every person summoned as a grand juror shall serve as such in the term for which he or she is summoned for such time or times as the court may require and until a succeeding grand jury shall be called and impaneled as provided by law.