With apologies to lowcostdolly and her colleagues, it's been some flights since I paid full attention to the safety briefing. It is a "show" I have seen before and on the third leg of the day I am less capable to bring up the concentration to watch attentively. However, I keep one ear open for airplane specific instructions (lifevest or seatcushion) and review the safety card.
Frequent flyers do know most of the drill and unless airlines start using a completely new model of belt-buckle, they'll know how to strap in and out. I think politeness to crew and new fliers requires that one shuts up to allow others to pay attention.