XF 2.0 Login expiring

Lukas W.

Formerly katsulynx
I've noticed that on my live installation, logins are expiring every time, someone stays away from the site for an hour or so, meaning they have to log in again on their next visit regardless of them checking "stay logged in" or not. I assume that the server isn't configured to hold the sessions for long enough or so? Someone maybe got a hint what is causing this behavior?