Changing up account names
Something I recently learned: not only can you (obviously) change your password at any time, but most places allow you to change your account name too. It's not a bad idea to do so every now and again.
Also, if you reuse account names, you might want to change that up so that if one site is breached it doesn't help people to hack into your account at another site. I.e. if you use HappyCamper95 as your account at Vanguard, maybe don't use that at Schwab, maybe use ClassBPeople there. It certainly doesn't hurt.
Vanguard actually makes this harder, they mention you can change it, but you have to call them to do it. Other banks and investment companies I've tried let you change it in the same place you change passwords.