“Opportunities, like eggs, must be hatched when they are fresh”

“Opportunities, like eggs, must be hatched when they are fresh” is an American proverb that has been cited in print since at least 1859. The saying means that opportunities don’t last long; like eggs, they spoil quickly.
 
A somewhat similar American proverb is “Opportunities, like eggs, come one at a time.”
   
 
Google Books
Here and Beyond: or, The new man, the true man
By Hugh Smith Carpenter
New York, NY: Mason Brothers
1859
Pg. 138:
Opportunities, like eggs, must be hatched when they are fresh.
   
20 June 1863, New-York (NY) Ledger, pg. 3, col. 5:
WIT AND WISDOM.
ORIGINAL AND SELECTED—PREPARED EXPRESSLY FOR THE LEDGER BY GEO. D. PRENTICE.
(...)
OPPORTUNITES, like eggs, must be hatched when they are fresh.
 
10 September 1863, Wooster (OH) Republican, pg. 4, col. 2:
Opportunities, like eggs, must be hatched when they are fresh.
 
22 October 1863, Berkshire County Eagle (Pittsfield, MA), “Pithy, Witty and Pat,” pg. 1, col. 2:
Opportunities, like eggs, must be hatched when they are fresh.
 
Chronicling America
27 April 1866, Fremont (OH) Journal, pg. 1, col. 7:
Opportunities, like eggs, must be hatched when they are fresh.