That's (ballpark) equivalent to 8 completely random characters, which is relatively hard to remember. I know, personally, I'd rather remember 1 word than 2 randomly chosen characters from a pool of ~100.
Easy to remember and easy to type.
What benefit does this have versus adding an additional word?
All my passwords are randomly generated, I set the minimum at 30 characters. My most important passwords are 40 to 50 characters.
I highly recommend a similar system. I feel a lot safer than when I had to remember passwords for my email accounts, banks, credit cards, Ebay, Paypal, my webservers, FTP, SSH.
I even store my credit card info in KeePass, so I don't have to type the 16 digits every time.
So if a single password is compromised, all of your randomly generated passwords are compromised? So what kind of password do you use for the keyring that you believe is better than memorizing a chain of words?
For reference, my longest pass phrase is a story constructed around ~30 random words, which using equivalency above, is about ~60 random characters. I don't have to rely on a password manager to keep it safe via a (probably weaker) password.
Anything beyond that is simply done via carrying a physical device with a key on it.
If you're using the printable ascii characters with fully random selection, that's 6.55 bits of entropy per character, for a total of 196.5 bits of entropy over 30 characters. For anything over 20 characters (=131 bits of entropy if randomly selected), you're implying that there is someone out there who can bruteforce the keyspace of AES (128 bits in the most common case), but can't install a keylogger on your system.
I also try to futureproof with using extra long passwords. Most of the time I copy-paste them anyway, so it doesn't matter.
The attacker wouldn't know which characters I used, so they will have to have a wider coverage anyway.
Keylogger is my worst fear, of course. But I try to be safe about the shit I download and how I browse the websites. I scan my PC for viruses, keyloggers and rootkits daily.