I've been doing some poking around on the Speed Demos Archive and Speed Runs Live ever since the Awesome Games Done Quick marathon and came across a listing of all 955 games currently being tracked in the archive. I just had to search for my favourite game Final Fantasy IV. I wish I'd made a guess for what I thought the top time would be but I bet I would have been a lot higher than the actual times!
I just went and checked my post from when I played the game in my own marathon and apparently my game clock was only around 14 hours. For some reason I was thinking it was more like 20. Hmm. Maybe I would have gotten close to the current record with my guess if I'd known that? It turns out they track the game in 3 different categories. The fastest single segment run clocks in at 3:21. The fastest multiple segment run is only 3:05. And the fastest run that _really_ abuses glitches so badly it got its own category was 2:17. The version closest to the way I've played in the past would certainly be the middle one, so only about 21% of my time!
There are three main things that let someone speed things up beyond what I'd have done normally. They know the precise route to take (including what treasure chests are worth picking up), they don't read the text boxes (which makes me a little sad because reading the story is the best part of a Final Fantasy game for me), and they run from practically every fight. Oh, and all the glitches...
I sat down over the last couple days and watched the 3:05 run while eating. It starts out pretty standard with the only real differences being they run from every fight, skip almost every treasure, and have timed out the boss fights so they know what attacks to use when. It wasn't until right after the fight with Golbez in the dwarf castle that the glitches were busted out but there were three of them used that drastically change the game. I had read about them all before so it wasn't a huge surprise to me, and I'm a little sad there wasn't anything new to see.
Glitch 1: If you cast warp right after that fight with Golbez you get sent back into the crystal chamber from the throne room. There is still a dark crystal there, which you can pick up. Having this crystal in your inventory means you trigger the end of the sealed cave when you walk into it which means you get to skip a dungeon full of mandatory encounters!
Glitch 2: Any given action in combat can only proc one trigger. Presumably this is to stop counter attacks or reflect spells from chaining infinitely. What it means is that if you bounce an attack spell off of your own walled character the damage done to the enemy won't trigger any of the monster procedures. In particular this means you don't have to fight all four fiends in the Giant of Babel... If you kill off Milan with reflected spells the fight just ends. I think this gets used on the CPU core and on Zeromus at the end of the game as well.
Glitch 3: If you use a life potion on an enemy as the enemy is dying you get the experience and loot for 2 kills. The run I watched used this twice, right before the four fiends fight, in order to power level Rosa and Rydia. He got into a fight with one of the alarm monsters that summons in an enemy if it's attacked while alone. Then he got into a cycle where Rosa would attack the alarm for mediocre damage causing it to summon a dragon. FuSoYa would cast weak on it, knocking it to 1 health. Cecil would attack it, killing it. While that animation was playing both Edge and Rydia would enter in commands to use a life potion on the dragon. 3 dragons worth of experience per round of combat! He had it timed out so he knew how many cycles he needed to do in order to get Rosa to learn the white spell and to get Rydia to learn the nuke spell. The other 4 characters were killed off to focus the exact amount of experience into the two that needed it.
One other way the game changed when playing at such a low level and while skipping every random encounter is consumable items go way up in value. Casters also go way up in value since they'll always have mana to do their thing. (Well, not quite... Most of the treasures he looted were ethers to keep the casters going!) The melee characters were complete trash which is a big change from the 'real' game where autoattacking was awesome. He rarely got new weapons for anyone and never got armour for them.
4 hours actually seems like the sort of time that is entirely reasonable for one of their marathon things. Plenty of other games came in around that time. Maybe it's actually worth trying to get really good at speed running Final Fantasy IV...