Global Password Policy changes and effects.

Hello Experts, I'm preparing to make changes to my Global Password Policy without a test environment available to me, and I'm trying to determine what happens when I increase the password length requirements. To be exact, I need to know when these would kick in after I make the change.

For example, after I increase the password length, will all accounts be forced to change the password immediately, OR will they need to do that when the next password expiration date comes around?

What about service accounts set to never expire? Those are my main concern, rather than standard users. Does the change trigger immediately, or after a reboot or login?

Any insights will be appreciated, thanks!