"Living in Sin" (title)
As we have mentioned before, the phrase "living in sin" refers to living with one's partner out of wedlock (not being married). The title leads us to believe that this couple is so in love that they just couldn't wait for marriage, and that they are rebels, going against the grain of society in the 1950s.
no dust upon the furniture of love. (2)
This is one of only two times that "love" is even mentioned in this poem. In fact, without this metaphorical association of love with the studio, we might not even recognize that this poem is about love at all! But thanks to this one line, we know that everything that is said about the studio applies in some way to the couple's relationship as well.
By evening she was back in love again,though not so wholly but throughout the nightshe woke sometimes to feel the daylight cominglike a relentless milkman up the stairs. (23-26)
After a whole poem showing the state of disrepair the studio (the relationship) is in, we might have assumed there was no love left in this relationship. But this second and final mention of love in the last lines of the poem shows that the woman still has feelings for her partner, which might be what keeps her in the relationship. However, we don't end on this positive note. We end on the anxious feeling the woman has that soon, the daylight will come and show her once again all that is wrong in her relationship.