I would guess that established metal bands face a quandary every time they begin work on a new album. By “established metal bands” I mean those who have put out enough records over a long enough period of time that they have a well-defined sound and, by metal standards, a large and relatively devoted fan base. I’m guessing, because I’m not in an established metal band and don’t know anyone who is. Fortunately, lack of first-hand knowledge has never held me back from expressing opinions.
Here’s the quandary: You can continue to do the same kind of thing you’ve done before. This is the safe route. You know you will probably please the die-hard fans, because you’re giving them what they’ve liked in the past. You’ll please your record label, because whatever pleases your established fan base most likely means predictable sales. And because it’s the same kind of music you’ve done in the past with success, you can be reasonably confident that you won’t fuck it up.
But maybe it’s not so safe. Because there’s a difference between writing good new songs that are recognizably YOU and… coasting. Coasting is risky, and I would guess (see above re my complete lack of personal knowledge) that it’s also boring for the people in the band. And when people in a band start to get bored, they’re on the brink of a death spiral.