Well, you make it a task to do so. I think the best way to listen to a group's full discography is to listen to it slowly and at your own pace.
I remember trying to gulp Formula of Love down all at once. It hurt. And I found that the songs didn't stick to me that much until after a while. It's like that for discographies but on a much larger scale.
I've listened to Twice's discography so many times, I could probably name them if you just play the intro. I don't remember how I listened to it all eventually but I know that when I revisit it, i always go album by album. And try to take it all in once again before I move on to the next.