If you're using a distro that uses a desktop derived from GNOME 2 you can use the application Caffeine to control when your system's screensaver and auto suspend kick in.
For GNOME 3 based distros you can use this GNOME shell extension, also called Caffeine.
Applet screenshot - shows enabled/disabled
NOTE: You can use it to control which applications will block the screen/suspend from occurring.
Applet's config dialog
untested by me
NOTE: I found this method in the comments of a Linux Journal article on Caffeine. Your mileage may vary with this solution, from what I understand,
setterm is for controlling similar features such as blanking the screen and powersaving, but from a console perspective, not an X windows desktop.
$ setterm -powersave off -blank 0
For permanent change Add to your
~/.Xinitrc file or whatever dot file is approprite for running these commands as part of your environment:
setterm -blank 0 -powersave off -powerdown 0
xset s off