Unbelievers have no opportunity in life to believe, and believers have no opportunity not to believe. Since we don't know who is who (God wisely hides this information from us), we herald to everyone opportunely and inopportunely.

The things God chooses in this world (including believers–especially believers) are despised by the world. The New Living Translation is not exactly my translation of choice, but it IS choice in its rendering of 1 Corinthians 15:28— "God choses things despised by the world, things counted as nothing at all, and uses them to bring to nothing what the world considers important."