Using Lubuntu 13.10 is a pleasure, but the screensaver (or power saving) settings have been a little wierd.
this post suggests doing it in the "default applications for lxsession"
What i've found is that you need to create a new file:
you will need to add a few things. begin each line with @
#start the power manager because 13.10 doesnt enable it by default
finally logging out doesn't seem to work 100%. I really don't understand why I have to reboot... but, reboot and you should be able to configure your screen blanking with the xfce4 power manager (in the start menu) instead of having x.org blank your screen. Also i like the xfce4 power manager battery management.
#turn x.org default screensaver off because we are using the xfce4 power manager
@xset s off
verify xfce4 is running with: (pgrep returns a pid)
verify xorg screensaver is off with (last line should be "timeout: 0" )
$pgrep xfce4-power- -lf
FYI 13.10 doesn't have an animated screensaver. If you want that you will have to install a screensaver, but I do not provide instructions here.
$xset q|grep Screen -C2