If, as I suggested below, reading and rereading Scripture produces an unending series of mini-epiphanies and insights into God's revelation of Himself to us, it also seems to be the case that which insight comes when is for the most part unpredictable.
So we're all going about with different sets of insights on, say, the parable of the tenants or Psalm 43, but we have no way of knowing whether (nor any reason to expect that) we have all possible insights up to and including our most profound ones. We're feeling pretty good about ourselves and our grasp on the parable or the psalm, then *pop* goes a rather basic and obvious insight that we had somehow missed before, which subtly alters all the more profound insights, and we feel like an idiot for never having noticed this basic and obvious thing before.
But we shouldn't feel like idiots for never having noticed it. The indeterminacy and unpredictability of what we're going to discover next is just part of the nature of encountering God's word. Rather, we should feel like idiots for feeling pretty good about ourselves and our grasp on the parable or the psalm.