Much like the Pixel 4, the Galaxy S20 won't stay at its high refresh rate all of the time.
According to Samsung, the Galaxy S20 is going to drop down to 60Hz in some circumstances, including when the battery gets low. This is so that it can conserve battery, and get you through the rest of the day.
It's not just when the battery gets low though
The Galaxy S20 will also revert to 60Hz when the battery starts to get hot. This is because 120Hz is going to use more power and make the battery hotter. So by reverting it back to 60Hz, it allows the battery to keep from overheating. And that's a safety thing, as well as making your battery last longer, in the long run. This is smart by Samsung, especially after the Galaxy Note 7 debacle.
When the battery reaches 42ºC or 107ºF, it will revert to 60Hz. That's not very hot, and it could reach that temperature pretty easily in the summer. But this is so that Samsung doesn't have another Galaxy Note 7 issue on its hands.
It will also revert to 60Hz in some apps. Now while we don't have the list of apps that will drop to 60Hz, we do know that they are apps that already use a good amount of power. Like the camera and Google Maps. And let's be honest, 120Hz in the camera app isn't really needed as much as it is in a game or even Twitter.
There are limits on 120Hz, but it's a good thing
There are some limits on the Galaxy S20 series using 120Hz all the time, and it's actually a good thing. Even though users may not like it much, the limits are designed to keep the Galaxy S20 series safe for users, and it is also designed to conserve battery. Both on a single cycle and throughout the life cycle of the phone.
Now, unlike the Pixel 4, there doesn't appear to be an option to force 120Hz all the time. And given how much the Galaxy S20 can do, that is going to be a good thing too. But, there's likely to be some kind of "hack" to get that option for the Galaxy S20 in the near future. That's something that always happens.
We'll learn more about this once the Galaxy S20 gets into reviewers hands in the next few days. Pre-orders for the Galaxy S20 series opens on Friday.