Almost immediately after we learn about how stunning and original and unique and generally awesome our speaker's double-ended candle is, we learn, of course, that it's not going to last forever. And that leads us right smack into a whole tradition of poetry that bemoans the impermanence of things. Life ends. Love ends. Even ice cream melts far too quickly. Unlike some of those gloom-and-doom poems you've read in the past, though, "First Fig" focuses on the bright side—literally. Her light may change into darkness very soon, but for now, it's radiant.
The speaker of "First Fig" emphasizes that her light's brightness is more important than its duration. It's quality over quantity, folks.
The short duration of the speaker's metaphorical light in "First Fig" makes its importance tinged with sadness. Sniff.