Legit, my old job required a 90-day change, and I once logged into a system I could do monetary damage on with ease, because I took a guess at my manager's password based on how long it had been since he told it to me during an emergency.

He did what every single person I spoke to did. "password 01" changed to "password 02" and I just tried twice, and sure enough he had changed it three times since he had told me.

While I wouldn't be ruining the company as a whole, I could have easily fucked over the individual location because scheduled password changes just ensure people use predictable passwords.