mingetty is configured to restart itself if logged out or killed, note that logging out is actually killing the process. This is due to the 'respawn' directive in /etc/inittab. If you feel that you don't need the default number of ttys, you can remove them. You can execute the following commands to remove them :
First of all you will have to put off the required number of lines as the below :
# telinit q (reloads inittab file)
# deallocvt /dev/tty[2-9] /dev/tty[0-9][0-9] (de-allocates the specified tty)
# rm /dev/tty[2-9] /dev/tty[0-9][0-9] (removes the ttys)
This would make the mingettys not starting...