Why do you think the last line of the poem is repeated twice?

In the poem ‘Stopping By The Woods On A Snowy Evening’ written by Robert Frost, we observe that the poet uses many poetic devices. The poetic devices used in the last two lines of the poem are repetition and symbolism. The poet repeats the last line because, although they are exactly the same, they each have their own meaning and symbolism.
In the first line, the poet means that he has to complete his duties and look after his responsibilities before he can go to sleep. In the second line, however, the poet means to say that he has to complete the duties and responsibilities assigned to him on this earth before he can have his eternal rest.

The last line of "Stopping by Woods on a Snowy Evening" is arguably the most important because it holds the allegorical key to the poem's overall meaning. Repeating the line emphasizes its importance. The scholarly consensus of opinion holds that the poem is an allegory on death and our attitude to the inevitable fate that awaits us all. In the last repeated line, Frost is encouraging us to realize that life is a journey, a potentially long one, at that, and one for which we must prepare. There are still many things left to do in this life before we die, many miles to go before we sleep. The final destination is the same for us all, but the journey in each case is different. It's the journey that's important, a point that bears repeating.