PSA: You can bank the Demonic Skull and still get the XP benefits.

I'm posting this because I see a lot of people (mainly ironmen) running wildy agility laps with the skull on their character.

You don't need to, you can enter the wilderness with the skull equipped. Then find a wildy banker and bank the skull with them and still get the XP bonuses as if you were still wearing the skull.

If you log out or hop worlds you will however have to reacquire the skull outside of the wildy and repeat the banking process.

This means you are not risking the cost of the skull each time.