I'll warrant that if you have hundreds of accounts you rarely log in to then it may behoove you to record them somewhere. However in this case I'm not sure a password vault is superior to just keeping them on an encrypted volume on a thumb drive. And I'd still argue its best to keep these rarely-used credentials siloed from your day-to-day passwords, especially if they're being held in trust for someone else (really each client should have their own silo).

That’s a good point about siloed credentials, I honestly never thought about that.

However I’d say give that the password vault is open-source and can be self-hosted (like Bitwarden) there are many reasons to use it over an encrypted flash drive. It can be automatically backed up easily, is supported on every device (including mobile) via a web browser. It also includes useful tools like a configurable password generator, versioning, and auto fill. For the average person that is much better than an encrypted flash drive volume, which IME are platform locked (LUKS doesn’t work on Windows, Bitlocker doesn’t work on Linux), are much less convenient, and are much more fragile.

Of course, use whatever works best for you, I don’t know your situation.

Sure, but for passwords you rarely use the added convenience of things like autofill seems less impactful compared to the added attack surface.