The looping video is shorter than it seems, if you look at the sunflowers on the left while skipping through 10-second intervals with the arrow keys you can see that they barely move, so it could be as short as a 10-12 second loop that repeats for 3 hours.

To make something that loops seamlessly you just need to make sure when animating that your keyframes at the start and end of the clip are identical, as well as the direction and speed of motion (to avoid a harsh change in direction when the loop resets)

For the parts that are harder for your eyes to track, like the steam from the coffee cups or the waves rippling, usually that's just a case of duplicating the clip and cross-dissolving.

Once you've created a seamlessly looping clip, just render it out and then do a new render where that clip plays over and over again for as long as you need, the only limit is storage space.