If we trust in God, we won't shrink from the possibility that God might be revealing truth to us gradually over time. In the Fourth Gospel, Jesus seems to suggest that revelation may be part of a journey toward truth, for which we need the Spirit as a guide: "I have much more to say to you, more than you can now bear. But when he, the Spirit of truth, comes, he will guide you into all truth" (John 16:12-13, emphasis added). I can't believe that that our Spirit-guided journey to "all truth" ended at Pentecost, or the Council of Nicea, or the Reformation, or any other particular time.
* * *
It's entirely plausible that God likewise might be gradually revealing things to us over time, in terms we can understand at any given moment. This would be consistent with the gradual progress of scientific knowledge, which some (I among them) speculate is a species of revelation.
I don't mean to argue that we should constantly rethink everything we know or believe, just in case God might reveal something new or different about it. That'd be like checking your email every 30 seconds on the off chance that someone might have sent you a new message -- you'd never get any work done.
But neither should we go to the other extreme, insisting that all of God's previous revelations to us must be fixed and immutable for all time. Indeed, it might be blasphemous to say categorically that God is not blessing us with additional revelation as we become more capable of handling it. At a minimum, our taking such a position would suggest that maybe we don't trust in God quite as much as we claim.
If we stay open to the truth, whatever truth turns out to be; work hard at the Great Commandment; and trust in God to take care of the rest -- what is there left to worry about?