I had my own little render farm of 3 computers, although they're getting old now, and my current PC is faster than all of them combined, so I just leave it rendering overnight now. I still use the render machines during the day though.
Back in the old days when my friend used to work at a high school, I used to use a whole room of their computers remotely to render. Good times!
The rendering exerience I have is catpoop compared to what you do but I have done some gaming videos in 1080p and I remember always getting annoyed when you come back after 30mins or so and watched your rendered movie and realize you forgot to edit some or sync some scene and you had to do it all over again. I'm guessing you are more careful when you render for several hours. Although your brain can only functions for unlimited amount of time meaning you'll come to a point when you just want the shit to be done and that's when things get out of hand.
My videos go through several different stages, so there's a lot to keep track of. And not only do I have to render off the frames from my 3D program, but then I still have to edit them together in After Effects and add effects and export from there, and that final video exporting stage like you go through is about the least of my problems.
The 3D rendering takes so long, that I really have to keep an eye on it to avoid mistakes, because I often don't have time to render long shots twice. It often has to be right the first time. Some shots I can render several times without any problem though. It can take several days continuous just to render off one shot of under half a minute.
I've gotten pretty good at avoiding any catastrophic mistakes, and pretty good at covering up the minor mistakes.