Assuming an random alphanumeric password and a 256 bit hash there is no benefit going above a 55 character password. Even if you aren't just using random characters I think 100 is a fine limit. Most people are not going to be using a password that long without a password manager. If they are using a password manager they might as well just use a random password.

For there to be more security in allowing passwords thousands of digits long the host would very likely being storing your password in plain text as opposed to pulling out a few thousand bytes out of an XOF (extendable output function).