That's nuts. I had to do 100-hour weeks a few times in my career, and felt that any time above that had zero or even negative productivity.

Is it really necessary to do so many slide decks in order for IB to be as productive?

That was basically my worst experience ever over the course of 7 years and I have never personally met anyone who's worked more ours in one week (lol?) but yeah, any "meaty" meeting is likely to generate a few hundred slides if you include all of the revisions, so it gets out of hand fast. I probably had 5-10 100-hour weeks in any given year, but an 70-80 hour week would be pretty normal

Shit compounds when there's a deadweight on the team, or a managing director that doesn't know what they want / has poor planning, or everyone's busy on other projects or the situation is actually complex. In that particular case, it was a combination of a deadweight analyst on a very lean team (I was the only associate, no VP, one very senior director trying to make MD and 2 other super senior MDs... for a $2B M&A deal), poor planning and an actually complex situation (crossborder, post-bankruptcy former public company with public debt still outstanding, multiple tax jurisdictions, CFIUS issues, you name it) leading up to a board meeting on Friday (to which I took a flight to deliver the books, which added to the hours...)