“As soon as you sit down to a cup of hot coffee, your boss will ask you to do something”

A “Law of Coffee” is:
 
“As soon as you sit down to a cup of hot coffee, your boss will ask you to do something that will last until the coffee is cold.”
 
The saying was called “Owen’s Law for Secretaries” and published in Arthur Bloch’s The Complete Murphy’s Law: A Definitive Collection (1990).
 
 
Google Books
The Complete Murphy’s Law:
A Definitive Collection
By Arthur Bloch
Los Angeles, CA: Price Stern Sloan
1990
Pg. 154:
OWEN’S LAW FOR SECRETARIES: As soon as you sit down to a cup of hot coffee, your boss will ask you to do something that will last until the coffee is cold.
   
7 October 2005, the Manila Times (Manila, Phil.), “Big Deal: Do we really need an antiterrorism law?”:
Law of coffee: As soon as you sit down to a cup of hot coffee, your boss will ask you to do something, which will last until the coffee is cold no matter how hot is your coffee is.
   
Google Books
The Book of Awesome Humour
By Sunil Bali
Milton Keynes, UK: Performance Publishing
2011
Pg. ?:
The Coffee Law
As soon as you sit down to a cup of hot coffee, your boss will ask you to do something which will last until the coffee is cold.
 
Google Books
The Biggest Joke Book Ever
By Jack Jacoby
Victoria, BC: Trafford Publishing
2012
Pg. 708:
Law of Coffee: As soon as you sit down to a cup of hot coffee, your boss will ask you to do something which will last until the coffee is cold.
   
Thought Catalog
JULY 6, 2015
Wake Up And Smell The 100 All-Time Greatest Quotes About Coffee
Lorenzo Jensen III
(...)
28. As soon as you sit down to a cup of hot coffee, your boss will ask you to do something which will last until the coffee is cold.
—Anonymous
 
Google Books
How to Study Rhinos
By Bayard H. Brattstrom with Martha A. Brattstrom and Mary E. Shipman
Outskirts Press, Inc. (outskirtspress.com)
2016
Pg. 52:
The Starbucks Law: As soon as you sit down to a cup of hot coffee, your boss will ask you to do something which will last until the coffee is cold.