Take a look at `setterm` (see `man setterm`). I think the '-blank' option is what you want. In /etc/rc.d/rc.M, there is the following:
# 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 could probably just change that parameter -- but note that if you upgrade your system, rc.M will get overwritten (well, actually, it would put an rc.M.new file in place which you would have to merge). It may be easier to just add a new setterm command in /etc/rc.d/rc.local to override that line.
Woah, WAY off. I probably should have refreshed my page before posting. I should also learn to open fewer threads and do less at once...[/edit]