Configuring OpenWrt to Automatically Reboot Every Week
A weekly automatic reboot improves stability, especially on Atheros chipsets. These instructions are written for OpenWrt 10.03.1, but they should work reasonably well on other versions.

To setup an automatic reboot, login to LuCI and go to the System tab.  Then select the Scheduled Tasks subtab.  This window allows you to edit the crontab file, which works the same way as a crontab file on a normal Linux system.  If you prefer the command line you can also access this file at /etc/crontabs/root.  Add the following line to the crontab (beneath any existing lines if they are there):

0 3 * * 0 reboot

The first number denotes the minute (0-59).  In this case, 0 represents the top of the hour.

The second number denotes the hour (0-23).  In this case, 3 represents 3 AM.

The third number denotes the day of the month (1-31).  In this case, * matches any day of the month, so this field is ignored.

The fourth number denotes the month of the year (1-12).  In this case, * matches any day of the month, so this field is ignored.

The fifth number denotes the day of the week (0-6) beginning with Sunday.  In this case, 0 represents Sunday.

The final item is the command to be run.  The crontab runs with root privileges, so it has power to reboot the device.  A full path, as well as arguments, can be entered here if desired.

# Reboot at 4:30am every day
# Note: To avoid infinite reboot loop, wait a minute
# and touch a file in /etc so clock will be set
# properly on reboot before cron starts.
30 4 * * * sleep 70 && touch /etc/banner && reboot