All I have heard are nightmare stories from everyone I know whom has interviewed at a FAANG(or the likes). It's crazy how disrespectful(and frankly insulting) these companies are to candidates, under the guise of trying to get the best. I would assume the best aren't sitting around on their hands for months waiting for offers, nor are they overly willing to be jerked around.
(Things are quite different for other not-so-sexy companies that need engineering talent.)
For those who decide to go for a FAANG job - maximize your time. Prepping for an interview at one, preps you for the others, with minor differences.
So try and set up interviews with them all around the same time, while you are well practiced. Throw in a few smaller companies somewhere in there too, with different interview styles. Schedule on-sites for your least-desired opportunities first, and consider them warm ups.