I've seen every surviving episode of Doctor Who (as well as some of the reconstructed episodes--I love Two and Jamie, so that helped). Personal best were some Classic seasons that I did blast through in a day. Some of those T. Bakers might have been two seasons a day.
I take that back. I still haven't finished Whittaker's era, though I finally did power through Capaldi's after semi-leaving the fandom. I joined the fandom right before series 5 started, so the Eccleston and Tennant eras got blasted through in about a week.
I was definitely going fast around the Pertwee/T. Baker/Davison eras. The '60s were actually some of my favorites (Ian and Jamie are legitimately two of my favorite companions), though I was watching before even the last batch of missing episode finds came in. Then the C. Baker/McCoy eras started giving me the sleepies and I only finished McCoy off years later. Note that after the '60s with 40ish half-hour episodes, seasons from the '70s until now are really half the length of a typical American series. You might see 26 episodes cut into around 6 serials, but those are half-hours. I've done all of The War Games (10-episode serial that ended the Troughton era) in a day easy multiple times because it's a favorite.
One time, I inexplicably pretty much just watched Amadeus on a loop for a week. It's a 3-hour movie and I probably watched it 30+ times in that week alone. Asperger's alert. When I was 8 years old, I watched Hocus Pocus 6 times in a day. Should've been a hint that I had Asperger's way back then. I have a history of this.
I hit my binge roadblocks when I'm starting to fall asleep during things. I mean, that happens when you stay up for over 24 hours or more (I've done 36 hours), but it's definitely noticeable when the binges are keeping you awake and when they're not. Marvel films most recently have been giving me the sleepies during all the bloated CGI action scenes. I tried. And nobody can blame that on my attention span (LOL). I literally have an easier time watching the most dated media you can imagine.
My all-time binge is still all of Buffy season 2 (yep, all 22 episodes) in a single day. Another one of my monster binges was the Star Wars Original Trilogy (theatrical release, baby) and Indiana Jones Trilogy both in a single day together.
I did watch all of Supernatural, Smallville and The X-Files (though I actually stopped watching that one in season 2, only to pick it up again months later and blast through the rest) in roughly a month each. Those are some of the all-time monsters in show longevity. The Buffyverse is similar due to having two very connected shows to the point where I long ago stopped separating them. Smaller shows I can blast through in days, not weeks.
I pretty much give up on doing anything else when I'm in binge mode. It's snuggle-up-in-bed time. And yes, 15 seasons will do your head in watched that closely together. I've done it. You're living and breathing it by that point.
