How to stop screen going black after 10 min

In Lubuntu it is an option in preferences called "Light Lock". It's annoyingly on by default.

Try installing :

sudo apt-get install xfce4-power-manager

then configure it in:

xfce4-power-manager-settings 

For a temporary fix pop into terminal and type:

xset s 0 0

and this should stop the 10 minute blanking problem, to make it more permanent, insert a line with the same command at the start of the /home/username/.profile file.