“If it wasn’t/weren’t for the last minute, nothing would get done” is a jocular saying that has been printed on many gift items, such as posters, mugs and T-shirts. “If it weren’t for the last minute, a lot of things would never get done” has been cited in print since at least 1978, when it was credited to Kirk Kirkpatrick.
 
“Nothing makes a person more productive than the last minute” is a related saying.
   
   
21 July 1978, Register-Republic (Rockford IL), Earl Wilson syndicated entertainment column, pg. B6, col. 3:
REMEMBERED QUOTE: “If it weren’t for the last minute, a lot of things would never get done.”—Kirk Kirkpatrick.
 
25 October 1983, The Oregonian (Portland, OR), “Loom artist, craftsman weave pleasure, profit into partnership” by John Guernsey, pg. MS3, col. 3:
He glanced at a slogan on the workshop wall—“If it weren’t for the last minute, a lot of things wouldn’t get done”—and went back to building a floor loom of 600 parts.
 
20 November 1984, Philadelphia (PA) Daily News, “A year’s worth of hang-ups,” pg. 49:
Like “The other line moves faster,” “If it weren’t for the last minute, nothing would get done” and “If you have watched a TV series only once, and you watch it again, it will be a rerun of the same episode.”
 
Google News Archive
20 December 1984, Milwaukee (WI) Sentinel, “How To…Coordinate A Large Holiday Buffet”, pt. 4, pg. 1, col. 1:
A sign hanging in the Murray kitchen appropriately describes how they do it: “If it weren’t for the last minute, nothing would get done.”
 
Google Books
The New Official Rules
By Paul Dickson
Reading, MA: Addison-Wesley
1990
Pg. 147:
Mel’s Law. If it wasn’t for the last minute, nothing would get done.
— Unknown, Radio call-in show, New York, N.Y.
 
Google Books
The Complete Murphy’s Law:
A Definitive Collection
By Arthur Bloch
Los Angeles, CA: Price Stern Sloan
1990
Pg. 106:
If it weren’t for the last minute, nothing would get done.
 
Google Books
The 2,548 Best Things Anybody Ever Said
By Robert Byrne
New York, NY: Fireside (Simon & Schuster)
2003
1,226
If it weren’t for the last minute, nothing would get done.—Unknown
 
Google Books
Over Goal!:
What You Must Know to Excel at Fundraising Today
By Kay Sprinkel Grace
Medfield, MA: Emerson & Church
2006
Pg. 50:
My secretary used to have a sign on her desk that said, “If it weren’t for the last minute, nothing would get done around here.”
 
Google Books
The Speaker’s Quote Book:
Over 5,000 Illustrations and Quotations for All Occasions
By Roy B. Zuck
Grand Rapids, MI: Kregel Academic & Professional
2009
Pg. 423:
PROCRASTINATION
If it wasn’t for the last minute, nothing would get done.