It has been 6 years since NIST told companies to stop doing this. And I'd be willing to bet there are more companies still mandating this than ones that don't.
My old job had that policy. I decided I would not try to remember my passwords. Instead I had I.T. on speed dial and I would just call them daily to change my password to the one I liked. They hated me. I don’t work there anymore. For unrelated reasons. I think.
I wish I only had to change my passwords every 90 days. That would be a dream.
I'll just have to refer to the unofficial password sticky note that everyone in the office shares containing all the usernames and passwords, and the date on which they were last changed, that was started less than a week after the password change policy.
It's hilariously insecure, but we just can't deal with the password load. It's too much work. We'd sooner be fired if we had to comply with the password policy.
And that's how you get rules put in place to not use a password that's similar to your old passwords. (I don't agree with such rules, just to be completely clear)
If you are forced to use long passwords, use book titles, song titles, character names, album names, TV show names, etc etc.