Check '/etc/rc.d/rc.M', near the top you will see:
Code:
# Screen blanks after 15 minutes idle time, and powers down in one hour
# if the kernel supports APM or ACPI power management:
/bin/setterm -blank 15 -powersave powerdown -powerdown 60
You can change these numbers as needed. I usually change blank to 30, which is more reasonable.