I have ~16 different passwords that I regularly use for various sites/accounts/etc. that I enter manually (without saves/password managers). Those are what I use probably on a bi-weekly basis. They do rotate and change every few months. There are a few that I just have saved in a text file that I copy pasta because I doubt that if anyone hacked me they would be interested in logging into those accounts. If anyone hacked those sites, they probably wouldn't be able to tell if my password was plain text or encrypted.
It finally got too messy to remember all the different variations of my passwords, especially because you need to enter them a lot of mobile devices these days. With all the breached websites out there and new hacks coming every week, I know my usernames and passwords -- or at least variations of it -- are floating around in hacker circles. I recently got a password manager and I like it so far. I was able to really make unique crazy passwords for all of the important accounts. The hardest thing was coming up with the main password.