At work we had to change passwords once a month. Imagine coming into work phones ringing madly (supposed to answer them in three rings), and trying to get new passwords sorted out under pressure was bound to lead to errors.
The system Helpdesk team were very patient. At one point I used a password with the month and a number but you could only do that for one year as it remembered.
How glad I am to be retired. Santander was the worst for complicated passwords, if you messed it up and it was a complicated code, you had to wait for a letter giving new codes.
I have three spread sheets. One for really confidential stuff, number coded for the site, the other for the passwords for number one. The third is for various other less confidential website logins.