With all the impending dread as the temperature drops (did you notice the temperature at the beginning of every chapter?) this feels more like A Game of Thrones than a young adult werewolf romance sometimes.
This isn't just a genius tension building technique. It's also symbolic of the constant passing of time--that tick-tick-ticking like a tell-tale heart, reminding us of time's passage and our unstoppable march toward death. Yikes. Shiver just got real, y'all.
The realization that he's not going to live forever hits Sam really hard. He wakes up one day and thinks, “I hadn't been shifting for that long. Where had my summers gone” (22.4)? It's especially difficult for him because this is a guy that let all his human years just fly by. Ruled by anxiety and fear, Sam was never much of an active participant in life, and now he doesn't have much left. Even though he makes the best of the few days he has, Sam eventually realizes he's going to lose Grace anyway. He says, “I'd found heaven and grabbed it as tightly as I could, but it was unraveling, an insubstantial thread sliding between my fingers, too fine to hold” (39.46). Sam's heaven is slipping away because he can't stop time. This image is similar to the sands in the hourglass slipping through Sam's fingers as the days of our lives pass us by.