After completion of the examination of jurors upon their voir dire, the parties and their counsel shall be entitled, upon request, to 15 minutes to prepare for jury selection; thereafter, during the selection of jurors, the court in its discretion, upon first warning counsel, may restrict to not less than 1 minute the time within which each party may exercise a peremptory challenge; a party shall forfeit a challenge by failing to exercise it within the time allowed.