It is one developer's path through a huge game, including optional stuff that still has story weight. Your run will be shorter if you only chase the yellow. It will be longer if you fish, fight, and ruin your honor bar for fun.
What 80 hours probably means
Rockstar games hide the real length in errands that do not look like errands. A conversation that changes a relationship. A stranger mission that bites you later. Nelson's number was framed with optional objectives that still have consequences, not 'collect 200 seashells'.
If you are the friend who only does story missions, you might land closer to a long movie season than to 80. If you are the friend who 100% GTA V, pack a snack. I am in the second camp and I am already clearing a week in November.
The map talk sitting next to that number
The same preview cycle floated Vice City at roughly twice Los Santos, and Leonida as a much larger state than Red Dead's map. I am treating those as studio-adjacent boasts until I can drive a border. They do match the feeling of the parachute shot: this is not a city with a desert taped on.
Length and size are cousins, not twins. A dense 30-hour city can outplay a 100-hour empty one. The hope, after the Extended Look, is that they stuffed the hours with people and weather, not with loading screens between icons.
How I would plan a first playthrough
Do not marathon it like a live-service battle pass. This looks like a game that wants evenings. Switch characters. Get in trouble. Go to the beach and waste time on purpose. If the relationship stuff is real, rushing it would be like skipping songs to finish an album.
Spoilers are going to be a pest in November. If 80 hours is even close to right, the internet will finish the story before you finish the Keys. Mute thumbnails. Play the couple. Touch grass in Leonida, not just on the timeline.