When such a trial has gone on for weeks and weeks, the defence, the prosecution and the judge will all "sum up" and by that time, how many jurors will have really "made their mind up" even though they probably wouldn't say so?

To go through all the "evidence" again is surely a waste of time and effort? If you've not "decided" by then and are finally swayed one way or the other by argument in the jury room, is your "decision" really reliable?