"Once you're over the hill, you begin to pick…

“Once you’re over the hill, you begin to pick up speed” is a jocular saying used by some seniors and also some runners. The saying was first used by American cartoonist Charles M. Schulz (1922-2000) in a Peanuts comic strip in May 1974.

The saying is sometimes credited to German philosopher Arthur Schopenhauer (1788-1860), probably because “Schopenhauer” appears before “Schulz” in quotations lists and someone originally made a simple mistake.

Wikipedia: Charles M. Schulz
Charles Monroe Schulz (November 26, 1922 – February 12, 2000), nicknamed Sparky, was an American cartoonist, best known for the comic strip Peanuts (which featured the characters Snoopy and Charlie Brown, among others). He is widely regarded as one of the most influential cartoonists of all time, cited as a major influence by many later cartoonists. Calvin and Hobbes-creator Bill Watterson wrote in 2007: “Peanuts pretty much defines the modern comic strip, so even now it’s hard to see it with fresh eyes. The clean, minimalist drawings, the sarcastic humor, the unflinching emotional honesty, the inner thoughts of a household pet, the serious treatment of children, the wild fantasies, the merchandising on an enormous scale—in countless ways, Schulz blazed the wide trail that most every cartoonist since has tried to follow.”

3 May 1974, Aberdeen (SD) American News, “Peanuts” comuc stript by Charles M Schulz, pg. 8, col. 1:
PANEL ONE:
FRANKLIN ARMSTRONG: MY GRANDFATHER HAS A BIRTHDAY THIS WEEK.

PANEL TWO:
PEPPERMINT PATTY: DOES HE MIND GETTING OLD?

PANEL THREE:
FRANKLIN ARMSTRONG: NO, HE SAYS IT DOESN’T BOTHER HIM…IN FACT, HE SAYS HE FEELS GREAT…

PANEL FOUR:
HE SAYS THAT ONCE YOU’RE OVER THE HILL, YOU BEGIN TO PICK UP SPEED!

Google Books
1,001 Logical Laws,
Accurate axioms, profound principles, trusty truisms, homey homilies, colorful corollaries, quotable quotes, and rambunctious ruminations for all walks of life
By John Peers and Gordon Bennett
Garden City, NY: Doubleday
1979
Pg. 48:
Barker’s Byword:
When you are over the hill, you pick up speed

Google Books
The Quotable Quote Book
By Merrit Malloy and Shauna Sorensen
New York, NY: Carol Pub. Group
1990
Pg. 15:
Just remember, once you’re over the hill you begin to pick up speed.
Charles Schultz

OCLC WorldCat record
Once you’re over the hill, you begin to pick up speed!
Author: Selma Jacob
Publisher: Santa Fe, N.M. : Health Press, ©1993.
Edition/Format: Book : English

OCLC WorldCat record
Once you’re over the hill : (you begin to pick up speed)
Author: Charles M Schulz
Publisher: [New York, NY] : HarperCollins, 1997.
Edition/Format: Book : English

OCLC WorldCat record
Over the hill and picking up speed: older women of the Australian Longitudinal Study of Women’s Health
Author: J Byles
Edition/Format: Article Article : English
Publication: AUSTRALIAN JOURNAL ON AGEING, 18, Part 3 SUPP 1 (1999): 55-62
Database: British Library Serials

OCLC WorldCat record
Over the hill, you pick up speed : reflections on aging (for anyone who happens to)
Author: Nardi Reeder Campion
Publisher: Hanover, NH : University Press of New England, ©2006.
Edition/Format: Book : English

Slate
MAY 19 2014 11:37 PM
“Hang in There!” –Arthur Schopenhauer
Quotation websites and the outsourcing of erudition.
By Mark O’Connell
Arthur Schopenhauer—the 19th century German philosopher for whom human existence was a perpetually swinging “pendulum between suffering and boredom,” and the world itself a hell in which “human beings are the tortured souls on the one hand, and the devils on the other”—tends to get pigeonholed as a fairly downbeat guy. But the author of such elegantly corrosive essays as “On the Vanity and Suffering of Life” and “The Fullness of Nothingness” is also apparently responsible for the quote that probably appeared on the inside of the card you gave your dad on his 50th birthday: “Just remember, once you’re over the hill you begin to pick up speed.”
(...)
The “over the hill” line is commonly attributed to Charles M. Schulz, creator of Peanuts—probably not because he is its original author, but because it’s used in one of his strips (it’s Franklin’s grandfather’s personal motto, apparently), and provides the title for a little book of Peanuts wisdom. The root of the confusion here is, I think, the alphabetical proximity of Schopenhauer to Schulz. If you’re listing quotations alphabetically, Schopenhauer is going to appear very close to—in fact likely just right above—Schulz. This is certainly the case here, where something that Schopenhauer actually wrote is positioned directly over the Schulz quotation, thereby suggesting a possible origin of this whole snarl-up.