Sorry to disagree, but Tomb Guards DO have to take a lifelong pledge not to drink alcohol. I’ll find the documentation for you.
The tombguard.org link above says that it is a myth.
http://www.tombguard.org/FAQ.html#Is it true they must commit 2 years of life to guard the tomb, live in a barracks under the tomb, and cannot drink any alcohol on or off duty for the rest of their lives.