Why does TFA take three days tops?
It doesn’t. It’s at least three days. Not that it matters terribly. And there’s a thread for this:
https://originaltrilogy.com/topic/How-much-time-does-each-movie-cover/id/50630
Movie time is weird.
We see almost one full day on Jakku, from the middle of the night to sunset. Then the next morning Rey takes BB-8 to town, and they escape. Within what seems like 20 minutes of escaping they are found by Han, and immediately thereafter they go to Maz’s castle, a trip that takes the length of their fussing over the hyperdrive and discussion of the map (which starts a pattern that Hyperdrive trips in this movie don’t take that long, generally). At Maz’s castle, they have time for a meal and then they’re attacked. After they go to the Resistance events happen rapidly, with Leia sending a scout ship to Starkiller before she even looks at the map from BB-8. But then she does and within the ensuing conversation the scout ship returns and they prepare their plan of attack, which again takes no more than a few minutes. Then they’re at Starkiller Base for the duration (a few hours, tops), then it’s back to the Resistance base. Maybe the third day happens after the destruction of the Starkiller, but it can’t happen too long afterwards because the First Order knows their location and would be rushing to prevent them from escaping their base.
So here’s how I see it, with large potential variations because movie:
Jakku - 1.5 days
Han to Maz - 3 to 5 hours
Resistance Base - 3 to 8 hours
Starkiller Base - 4 to 7 hours
Resistance Base - 2 to 16 hours, depending on whether or not night passes between scenes
So the lower bound of that time is two days, with the potential for 3 at the upper bound.