אֵ֠לֶּה הַֽחֻקִּ֣ים וְהַמִּשְׁפָּטִים֮ אֲשֶׁ֣ר תִּשְׁמְר֣וּן לַעֲשׂוֹת֒ בָּאָ֕רֶץ אֲשֶׁר֩ נָתַ֨ן יְהוָ֜ה אֱלֹהֵ֧י אֲבֹתֶ֛יךָ לְךָ֖ לְרִשְׁתָּ֑הּ כָּל־הַיָּמִ֔ים אֲשֶׁר־אַתֶּ֥ם חַיִּ֖ים עַל־הָאֲדָמָֽה׃
Dies sind die Satzungen und die Vorschriften, die ihr beachten sollt zu tun in dem Lande, das der Herr, der Gott deiner Väter, dir gibt, es zu besitzen alle Tage, die ihr lebet auf dem Erdboden.
Chizkuni
אלה החוקים, “these are the statutes;” whenever the Torah commences a paragraph with the word אלה, this means that what follows is not a continuation in some form of what had preceded it. In this case too, the subject of the function of the two mountains Gerizim and Eyval are not connected to what follows. The commandment to be performed on or near these mountains, were one time only commandments. The places near there on which the gentiles had worshipped idols had to be totally destroyed.
Sforno
אלה החקים והמשפטים אשר תשמרון...-לרשתה כל הימים, observance of all the commandments listed forthwith is, among other things, a condition to ensure that you will remain ancestral owners of this land for all time. כל הימים, during all the time when you are busy wiping out locations dedicated to idolatry and you will not yourselves worship idols by becoming like them by offering your sacrifices wherever it pleases you.
Or HaChaim
לרשתה כל הימים, "to possess it for all time, etc." Moses simply meant that if the Israelites were to keep G'd's commandments then their tenure in the land would continue for ever.