“Junk is something you keep for years, then throw away two weeks before you actually need it” is a jocular saying that has been printed on many images.
 
“Junk: Something you keep ten years and then throw away about two weeks before you need it” was printed in the Gage (OK) Reporter on October 21, 1954. “JUNK—Something you keep ten years and then throw away ten days before you need it” was printed in The Jackson Hole Guide (Jackson, WY) on October 21, 1954. The joke was popularized in the Reader’s Digest.
 
       
Newspapers.com
21 October 1954, Gage (OK) Reporter, pg. 1, col. 3:
Definitions with a difference:
Junk: Something you keep ten years and then throw away about two weeks before you need it.
   
Newspapers.com
21 October 1954, The Jackson Hole Guide (Jackson, WY), “Riding the Range” by Floy Tonkin, pg. 15, col. 1:
Definition
JUNK—Something you keep ten years and then throw away ten days before you need it.
   
28 November 1954, Illinois State Journal and Register (Springfield, IL), “Assorted Smiles” by V. Y. Dallman, pg. 6, col. 3:
THE READER’S DIGEST’S “Definitions with a Difference” department prints these—Junk: Something you keep ten years and then throw away two weeks before you need it.
     
Google Books
Railway Carmen’s Journal
Volumes 59-60
Pg. 27:
Junk — Something you keep for 10 years and then throw away two weeks before you need it. — Capper’s Weekly.
 
24 August 1956, Evansville (IL) Courier, “Paragraphy” by Jroy, pg. 12, col. 1: 
Junk is something you keep for years and finally throw away the day before you need it.
 
Newspapers.com
11 October 1956, The Journal-Tribune and Shopper (Williamsburg, IA), pg. 8, col. 7:
Junk—That’s something you throw away just two weeks before you need it.
   
Newspapers.com
10 November 1959, >i>The Guthrian (Guthrie Center, IA), ‘Daffynitions,” pg. 6, col. 2:
Junk—Something you throw away a week before you need it.
 
2 August 1960, Pittsburgh (PA) Press, “Culch Pile” by William A, White, sec. 2, pg. 21, col. 2:
But I have heard a definition of junk. It’s something you throw away a couple of days before you need it.
 
Newspapers.com
17 May 1962, The Herald (Calgary, Alberta), “COnfidentially” by Bob Shiels, pg. 17, col. 1:
Junk is defined as something you throw away tow weeks before you discover that you need it.
   
Google Books 
1971, Boys’ Life, “Think & Grin,” pg. 98, col. 3:
Daffynishion: Junk—Something you save for years and then throw away just before you need it.—Sharon Jarosz, Parma, Ohio
     
Google Books
Another Treasury of Clean Jokes
By Tal D. Bonham
Nashville, TN: Broadman Press
1983
Pg. 55:
JUNK — Something you keep for years and throw away just days before you need it.
 
Google Books
More Clean Your House & Everything In It
By Eugenia Chapman and Jill C. Major
New York, NY: Penguin Group USA
1985  
Pg. 66:
Junk: Something you keep ten years and then throw away two weeks before you need it.
 
Twitter
ren_ren
@reneesingson
Junk is something you’ve kept for years and throw away three weeks before you need it.
10:18 PM · Apr 6, 2008·Twitter Web Client
   
Google Books
5,000 Great One Liners
Compiled by Grant Tucker
London, UK: Biteback Publishing Ltd.
2012
Pg. ?:
Junk: something you keep for years and throw away two weeks before you need it.
 
Twitter
Wings Hypnosis
@WingsHypnosis
Junk:  something you keep for years then throw it away two weeks before you actually need it.
8:01 AM · Jan 12, 2020·Hootsuite Inc.