recent OS update, now my screen goes dark in five minutes

In addition to the settings that P. Phillips showed, and especially related to the being logged out part, you should look at the System Preferences->Security & Privacy->Advanced. There a setting for "Logout automatically after...".

Like P. Phillips, I am running Ventura, so the looks are different, but the principles are the same.

System Preferences >> Lock Screen.

Adjust the settings for " Start Screen Saver when inactive " to a lower period of time

Adjust the " Turn display off when inactive " to a longer time

Adjust " Require Password after screen saver begins or display is turned off "

According to this Apple support page, the settings should be pretty much as we discussed, in the System Preferences->Energy Saver, in the case of a desktop mac, like the iMac:

Change Energy Saver preferences on a Mac desktop computer – Apple Support (UK)

https://www.lifewire.com/change-mac-screen-timeout-6499764

Excellent 👍 catch by @ Luis Sequeira1

Yes running Ventura in my Screen Shot - my bad for not mention this

I am not sure but I think that you need to click on the Privacy tab to see the Advanced… button.

Welcome for a collective effort from all those participating in this question.

 Thank you too 😀

Do come back to the Apple Support Communities ( ASC )  in the future  if / or when additional questions may arise.