The Torah Spring Edited by Shlomo Katz Devarim Vol. He explains that while much of Sefer Devarim appears, at first glance, to be repetitive, there is good reason for this repetition. Although Moshe had rebuked Bnei Yisrael throughout the 40 years in which he lead them, they were eager to hear more reproof in order to constantly improve themselves.
Many people use their last days to appease their opponents.
Two of the Torah's 613 mitzvot appear in Parashat Devarim. In it, Moshe repeats the mitzvot which are most necessary for the generation that will enter the Land. He warns them repeatedly regarding these mitzvot and scares them with threats of punishment. In some cases he offers additional explanations of the mitzvot. Regarding the mitzvot which apply to the kohanim, however, Moshe does not say a word.