I've sent out thousands of changes for code review and done reviews on many hundreds of changes. It's kinda weird to read this RedHat post on code reviews. I can't really imagine what the review process is like without things like the Google C++, Python and Java style guides (I haven't done Go, sorry Francesc). Things like that and required automatic formatting rules take a lot of the pain out the review process. But I have had changes that have taken more than a year to get into a code base. That does get a wee bit tiring sometimes.
https://lwn.net/Articles/709384/ Pythonic code review (Red Hat Security Blog)