xset command (from a terminal/xterm/whatever) to turn off the default X11 system screensaver. (Yes, another screensaver setting... this one is a feature from days of yore)
You should be able to put
xset s off in your .xinitrc or perhaps in your Window Manager's startup queue.
xset can manipulate many more X11 things, but
q are my most used options.
You can supply a command-line option to
X to turn off screen blanking from the beginning, but that can sometimes be more trouble to discover WHERE to add the option. Honest, it's do-able, just not obvious.
As an additional thing, you can disable the blanking of the text/console too (very handy on my Raspberry Pi's with no keyboard attached)
setterm -blank 0
This turns off the (also 10 minute!) console blanker. I place this command in
/etc/rc.local so it is set during boot, affecting everything thereafter.