"I hear you started dating some new girl."
"Yeah, but she's moving across the country in a month, so we're planning on breaking up."
"A little expiration dating, eh?"
When a woman is past her prime and looks it, but still tries to present herself as young and desirable. This might mean that she uses make-up tricks, botox, lip injections, etc. to appear more youthful to attempt to shave years off her age.
Many celebrity chicks over 40 are past their expiration date, but spend a lot of moneytrying to look like they are 5 - 10 years younger.
Hipsters and wannabe urbanites who move from suburban wastelands to NYC believing they will make it big in business, Broadway, or some other NY industry. Eventually, these mid-western suburbanites leave NYC generally after 1-2 years, after they realize they can't take the fast paced culture of NYC, get frustrated, and move to a more laid back city out west (Los Angeles, Seattle, or even back home). Those who expire are generally replaced with another hipster-suburbanite, who will eventually reach his/her expiration date, and the cycle continues.
Hipster E. village kid from Washington: Hey wheres Thom?