Ubuntu: visudo problem / NOPASSWD option does not work for commands

It is always the same:
After installing a new Linux commands like

/usr/sbin/s2disk
/sbin/reboot

only work with entering your password everytime (or precisely: after every reboot).
This can be changed with visudo:

export EDITOR=vi; visudo

 Inside the /etc/sudoers.conf you will see:

# User privilege specification
root    ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

And this is the problem:
First idea is to double the line

root    ALL=(ALL:ALL) ALL
schroff    ALL=(ALL) NOPASSWD: /usr/sbin/s2disk

and do the desired changes.

BUT: This will not work!

You have to add your line at the end of the file and after you exit vi (or whatever editor you have configured) it will work...