Most things I give up pretty soon, at least look up a walkthrough or ways to cheat it.
Only games I play hardcore tend to be racing. It's hard to put a number on that as there's often different events to try (unless you're in the very last thing left in the game), so I'll try this for a while, that for a while... But surely there have been many thing's that took at least several hours.

Then again,it took me 15 years to beat the Gauntlet mode of Wing Commander Academy, at least 100 hours of actual play time, but more likely several hundreds.

I'll still say that the game is worth it.  It's so good.  But the end is a huge spike in difficulty and definitely a roadblock for those who don't want to put in that extra time and effort to conquer it.

I used the mod because it would have added 10-15 hours of gameplay to have to fight that boss rush (which I could easily beat every single time) before every attempt on an extremely difficult boss.

Nowadays only a few hours.

When I was younger and had tons of spare time I would spend days trying to power through.

I think they're talking about the secret after you beat the game boss.  The final boss was easy, at least I thought it was if I'm remembering right.

my memory’s a little weak, but iirc, I’ve spent as long as 12hr on a single boss on several occasions. Can’t remember what the bosses were…I feel like one was from TLOU? Unsure.

I think your question is a world in itself. Because, if I'm having fun, I just tend to not give up. If the difficulty spike is just made of cheap tricks like unbearable HP limits and spamming for enemies and so, then it sometimes stops being fun and that's when I usually quit. I wouldn't in the past, but now time is much too valuable to not be having fun.

Most recent example I have to illustrate my point: this February I finally decided to play Dead Cells. The difficulty levels rise every time you collect a Boss Cell (BC), and then you play harder levels by accumulating BCs. So, a 0 BC play is your basic initial mode and so on from 1 BC up until you you get to 5 BC. I got to 5 BC, and from the builds you can make (Brutality, Tactics, Survival) the one I enjoyed the most was Tactics (you are more frail, but can kill from a bit more afar, so it is nice to think about the approach in each section of enemies, so taking your time pays off). Like I said, I got to the pretty hard end, getting to 4 BC in about 4 days and another 2 days to get the final one. As far as I could check on Reddit, apparently this was quite fast because of the nature of the game (get to the boss, die, get back to the whole start), but there you get to the ultimate run, "Hell", which is playing the game with all 5 BCs activated. And then there happened a case of very poor optimization, because the strategy I had had for all the previous stages became a real PITA, because the longer you take to clear a given area you are in, the more of spawns of super powerful, repetitive, HP sponge enemies keeps happening, rendering tactics pretty much useless. I pushed up about some good 4 or 5 tries, and gave up because the game was now forcing me to play "Ninja but not Ninja" (as in quick and deadly, but not silent, tactical, and deadly), forcing me to opt for full brutality mode if I wanted to move on. Killed all the fun for me.

For me, it depends on how fun the gameplay is.

FromSoft's Souls games are slow and just not fun to me. I can't say the same for Armored Core 6, though. It's fast and the action is much more appealing and fun to me.

So, every character in Octopath had its own final (Chapter 4) boss.  So 8 "final" bosses.  But then you do some shit and unlock the REAL final boss. So I guess it depends on what you consider the final boss.  But the true conclusion to the game was only seen after this stupidly difficult boss.

I don’t actually think of it in terms of time. Because it’s variable, on how much I actually want to play the game still. If I don’t really care about the game, I might stop after 1-2 defeats. Otherwise, it might be hours and dozens of attempts.

I recall the first time I played through Xenosaga Episode 2, I must have fought the Patriarch about 15-20 times, and finally won. The reason is I wanted to see the story, and the battle, while difficult, wasn’t exactly boring, even though it was one of the more annoying RPG battles I’ve fought - I’m not a big fan of these sorts of puzzle battles; but I didn’t need a guide, I needed a strategy.

On the other hand I quit every 3D Zelda game after Ocarina and before Breath of the Wild all on the exact same sort of thing: a lost key/switch/door somewhere in the vast maze. I mean, I could have easily looked it up, but after a few times “looking it up” the game loses its appeal to me and becomes a chore of following instructions to get through content - and that breaks the spell of the game, and it all becomes zero fun for me. I mean, if I wanted more following instructions to get things done, I’d pick up more work and get paid for it.

I liked that movie, its fun.