Singing a love story

It's been years since I heard Bill Morrissey's song "Birches" for the first time. I'm not sure what reminded me of it yesterday, but I found myself going to YouTube and searching for it. Turns out it's just as beautiful as I remembered it to be. The story he tells through song about an older couple whose relationship has lost the passion of young love, is incredibly moving. As they sit alone, the wife tries to reignite the spark, but the husband who's more practical dismisses her attempts in favor of what they have gained after so many years of marriage. Oak will burn as long and hot as a July afternoon, And birch will burn itself out by the rising of the moon. 
Still, after he goes off to bed, she dismisses his insistence to add oak to the fire and adds birch instead. The memories come flooding back and for a brief time, she is young again. And the shadows they saw nothing but a young girl on her honeymoon.
The last line brings everything into focus: She thought of heat. She thought of time. She called it an even trade.
Although the wife misses the way they once were, she also realizes that what she has now is lasting, that it is important, and that her husband's love for her will keep her warm through the cold winter nights.