Caducidad translates to "expiration" or "obsolescence." It's a word commonly associated with products or food, referring to an expiration date.
In this song, it's used metaphorically to describe how youth itself has an "expiration date" or a "shelf life." The singer warns his former lover that her youth, which she used to leave him for a younger man, will eventually run out, implying that he will be there when she realizes this. This unexpected and poignant use of the word makes it particularly interesting and memorable.
Grab a seat at the bar for this classic tale of heartbreak and hope. The singer sets the scene in a cantina, ordering two tequilas for a very specific purpose: one to remember the woman he loves, and the other to forget how she betrayed him. He tells us he gave her everything, his love, his heart, and his passion, only for her to leave him for a younger man.
But this isn't just a sad song. The singer is filled with confidence, certain that she will return to his arms. He believes she will eventually realize that youth has an "expiration date" (fecha de caducidad). The heart of the song is his bold prediction: she will come back crying once she understands that "two loves of 20 are not the same as one of 40." It's a powerful statement about the value and depth of mature love compared to a fleeting, youthful romance.