I can't say I have the exact same problem because I'm on a desktop machine but I have noticed that the power management in general seems to be broken. For example, in XFCE power manager I have the screen to blank at 15 minutes, sleep at 25, and off at 35. Even after many hours it never even blanks the screen.
Fresh clean Xubuntu 15.10 install here. Tried on 3 different desktop machines with various hardware (some UEFI, some old BIOS, some nVidia, some AMD) and the power management doesn't work on any of them. I also notice that for some reason the GNOME power manager is installed. Maybe it was pulled in by some other package? (not sure which but I do not have the gnome or ubuntu desktop installed, only xubuntu). It does not appear to be running though. I have these processes running related to "power": /usr/lib/upower/upowerd xfce4-power-manager --restart --sm-client-id 2f123... /usr/lib/x86_64-linux-gnu/xfce4/panel/wrapper-1.0 /usr/lib/x86_64-linux-gnu/xfce4/panel/plugins/libxfce4powermanager.so.. /usr/lib/x86_64-linux-gnu/indicator-power/indicator-power-service xfce4-power-manager-settings -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1511402 Title: Xubuntu not suspending on lid close To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xfce4-power-manager/+bug/1511402/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs