Deuteronomy warns that we not only must first "love YHWH our God," but we must also observe (the Hebrew can also be translated "hear") God's "commandments, decrees, and ordinances." I would include within those three different words much more than a series of legal demands. We need to hear Deuteronomy 7:7-8 just as much, if not more, than we need to hear Deuteronomy 5:1-21, his list of the Ten Commandments. If our lives are to be long in the land of promise, we must first love YHWH our God. Why? Precisely because we are first loved by that same YHWH! "It was not because you were more numerous than any other people that YHWH set a heart on you and chose you -- for you were the fewest of all the peoples. It was because YHWH loved you and kept the oath sworn to your ancestors, that YHWH has brought you out with a mighty hand, and redeemed you from the house of slavery, from the hand of pharaoh, king of Egypt" (Dt. 7:7-8).
The first word of YHWH is not a demand to follow a set of laws; the first word of YHWH is to respond to the love YHWH has freely offered to the helpless people enslaved in Egypt by first loving God and then, out of that rich love, following the commandments that God has lovingly offered the people. This is exactly why the first commandment of the Ten is the first: "I am YHWH your God, who brought you up from the land of Egypt, out of the house of slavery" (Dt. 5:6). That, of course, is no command at all; it is a loving restatement of God's first and greatest act for Israel, the people of God's choice.
And now we may hear the language of Deuteronomy 30 in a new way. If you love, and obey, and observe all that God has offered and given for your richest possible life, you will surely live long in the land that God has given, because you will be living in the hopes and promises of God for justice and righteousness for all of those who have received God's promises, namely all of our brothers and sisters. Long life now equals rich life in community, and prosperity means being rich toward and with God who has chosen us and loves us first and always.