Last year, I wrote a blog post about why I think half-hour meetings suck. You should read it first before reading this one – it’s short. Also, I still stand by a lot of it.
The tl;dr is that most things that require meetings actually take 15 minutes, 45 minutes, or an hour, and that almost everything else shouldn’t be a meeting in the first place.
I am now going to elaborate and add a whole bunch of caveats.