Okay, so the title is not technically accurate. I'm actually up to 24 hours. I meant to stop at 20, but I just got so caught up in doing diversions and side activities that I lost track of time. Running around the virtual city, sprinting up the sides of buildings and gliding across rivers, is just too much fun. As is using the wide variety of silly alien weapons and ridiculously strong super powers. I love to stomp my foot and send out a gravity wave that suspends enemies in mid-air, rendering them helpless targets for my disintegration ray.
My one complaint about the game is that I don't like that it takes place in a simulated reality. It makes all the alien technology seem unreal in the context of the setting. Yet I'm fairly sure it's not meant to be. Zinyak had telekinesis in the real world, so why couldn't the Boss?
That's a nitpick, though. I'm pretty sure that the "aliens stick the Boss in a virtual world" thing is just a money-saving measure. It allows them to reuse most of the Steelport map and most of the vehicles and random npcs from SR3. Which, okay, is kind of cheap, but I'm willing to overlook it because it's likely that without these cost-cutting measures, there wouldn't even be a Saints Row IV.
And that would be a shame, because it is a wonderful virtual playground full of interesting stuff to do, so much so that I've played it for 24 hours and have barely touched the main story. All I've really done is rescue my various Saints and then completed their loyalty missions. These are uniformly pretty great. Each one is a mini-narrative that explores some aspect of the character and is usually based on some central comic conceit. For example, you rescue Johnny Gat by going into an old-school side-scrolling beat-em-up. You earn Matt Miller's loyalty by playing out his NyteBlayde fanfiction, etc.
These episodic missions contribute to the game's overall "hang-out" vibe. You spend a lot of time getting to know your homies and very little on the details of Zinyak's plans or the culture of the Zin. It makes for a less than compelling science-fiction story, but a pretty fun and breezy sci-fi-themed comedy.
I'm pretty sure I'm close to the end, though. It's hard to say, because it's been years since I last played the game, but I think that the recruitment and loyalty missions are the bulk of the game, and the actual main plot is very short. I could be wrong, but I don't expect to take more than 2 or 3 hours getting through the rest of them, and then I'll have to think about whether I want to do the DLC missions (spoiler alert: I do).