I like your analysis of the poem very much. I agree with you that there are binaries between men and nature, life and death, and also mortal and eternity. It is very good to point out the comparison between the first few lines (youth, energy and life) and the last few lines (lifeless, dying...) in each stanza. And also the pattern of run-on sentences which represents the eternal power or existance of nature. In my opinion, i think that the pattern of the whole poem which divided into four stanzas and each stanza represents one season in a year can suggest a kind of circulation or immortal power of nature. Although "sick leaves" fell down, "rotten rose is ript from the wall," they will re-birth when the spring comes. However, if man is getting older and older and then finally die, he can not re-birth like leaves and roses again.