Four years. That's a Presidential office term.
That's the time between one Summer Olympics and the following Summer Olympics.
When the first post went up on June 1, 2010: Emily DiDonato, Chanel Iman, and Samantha Hoopes were all 19 years old.
Valerie van der Graaf, Emily Ratajkowski, Cris Urena, and Sara Sampaio were 18.
Kate Upton and Bregje Heinen were 17.