While I agree that usually a jury selection will take a day, or even only a few hours, with trial starting the next day. The pool assigned to the judge is for more than one case and they impanel the first qualified group, then move on to the next case while working through the pool numbers.
However in a “major” case, typically the judge here will get assigned a pool solely for that case, and the judge will have reviewed the questionnaires ahead of time, in order to start out by removing those who have conflicts, know personally any parties to the case, etc leaving the pool of potentials who can be questioned as to potential bias and challenged for cause, etc.