tty

With KDM, when a tty remained unused it expired.
E.g. when I start a new session on tty8, but change my mind before actually login in, and go back to tty7, the tty8 login screen will remain there unused for ever.
If I then go to the K-menu and try to start another new session, the tty8 session is not reused. Instead we go to tty9.

KDM handled this more gracefully, by allowing unused tty sessions to expire after a certain time if 1) there was no successful login and 2) the user switched back to another session.

An apparent regression compared to KDM in KDE 4, is that KDM used to remember which user last logged in on the current tty.

I regularly open two, sometimes 3 sessions, and they are usually ordered in the same way.
I open my main session in tty7. I would often open a secondary session in tty8, and more rarely a 3rd one in tty8.
The main session in tty7 would always be the same user.
Most of the time, the session in tty8 would be a different user than in tty7, but the same one.