Another point possibly relevant to this question is the Jewish idea that a bad decree can change, but a good decree cannot. @Fred provides the source:
"The Rambam says that a negative prophecy against the Jewish people is subject to change but that a positive one is not (Hil. Y'sodei HaTorah 10:4, English translation). The Rambam's sources that a positive prophecy for the nation is irrevocable are B'rachos 7a and Yirm'yahu 28:9."
The nature of prophecy, how we test it, and how we know whether to believe it are discussed productively here. Fred adds to these remarks that the Lechem Mishneh "defends the Rambam by limiting the case of an irrevocable positive public decree to wherever at least one of the following conditions were met:
The prophet stated it explicitly and in God's name.
The people did not relinquish their merit through sin."
A possible exception to these laws of irrevocability is an incident in Chapter 9 of Ezekiel, about which Rav Acha b'Rebbi Chanina says in Shabbos 55a, "Only once, Hash-m said to do something good and retracted." In this incident, Hashem seems to promise to protect certain group of righteous men from slaughter (Y'chezkeil 9:4), but then they are slaughtered anyway (Y'chezkeil 9:6). The Talmud interprets this incident as G-d's revoking His promise. But Fred points out that depending on how one reads the verses, it may be understood that those who were slaughtered were not essentially included in G-d's original protection, suggesting that this need not have been an outright revocation of the decree.
Presumably, the covenants mentioned in this question fall under the above conditions as "irrevocable positive decrees"--although the question of whether we have, or could still, relinquish our merit through sin (ch"v) is a good one.