I usually try to stay close to the instructions, but pretty often I end up turning up the brightness slightly later on. I just find it very unpleasant on the eyes when a game gets dark enough that it becomes a hard time to see ahead of you properly, so unless that's part of the gameplay (like horror or stealth stuff) I prefer to turn it up a little. Really depends on the game though, some games just have the balance right from the get-go, but then you run into a game like Borderlands 3 where I feel like I have to turn up the brightness at inside locations and down again at outside locations every time.