Jim Davis has an interesting take on viewing Proverbs as promises here. He suggests that proverbs, "set the bare minimum for what the Christian can expect." But I am not sure the dichotomy that Davis sets between "probabilities" and "promises" are the only options. I would prefer the idea of principles rather than promises. That is, if one follows a line of true wisdom, then the aspect of life covered by that wisdom is more skillfully navigated. Wisdom as a genre does not typically operate with mathematical precision.