Why does God take some people to Heaven prematurely—before it seems He should—and others so late when they are old and in such pain?
Isaiah 55 says God's thoughts are higher than ours. He has purposes we can't comprehend. I have seen marriages healed and siblings become sold-out believers through the death of a child or teenager. When I first answered this question a few years ago, a friend was holding her eighteen-month-old son in her arms, waiting for him to breathe his last. She was praying over him, reading Psalms aloud, trying to comfort and prepare him—and herself—for what was to come.
Who knows how many doctors, nurses, and patients were profoundly impacted by this child's ordeal? Who knows what family members turned to Christ?
Little David's life was just as long as God knows is best. I can't explain His purposes, and no explanation can or should remove a parent's grief. But I do know God's ways are best, and one day we will have a much clearer picture.
I have also seen older loved ones suffer who—for their sake—I wished God would take home sooner. But God has a purpose for them up to their last moment of life. Once again, the impact on family members of a godly person who faces disease and death can have effects we can't measure. It can produce in them a Christ-likeness that couldn't have been otherwise achieved.
Often God uses waning health and vitality not only to increase impact on others who benefit by caring for the elderly (my father and I gained a much closer relationship in his final years, when he needed my help), but by preparing the sick and elderly for Heaven. It is easier to let go of this world when there is no realistic hope that our health will improve, but only get worse. Now the whispers of Heaven become glad shouts of invitation: "Come here, where all will be right—not again, but for the first time!"
As the blind relish the promise of sight, and the lame the promise of full mobility, the sick long for health, and the old long for the fresh vitality of youth.
As loved ones go through great difficulty, we too are weaned from desperately clinging to them. I would never have considered taking measures to end my dying parents' lives, because I would not dare play God. But in both cases I was able to say, "If this treatment might add two months to their lives but make that two months more miserable for them, please withhold it and do everything you can to make them comfortable."
In stark contrast, many today seem eager to usher parents into eternity. I have heard people speak of their "inheritance" being wasted on care for their terminal parents. "Honor your father and mother" is a command we should take seriously. God enforces His commandments—the consequences of denying loving care for our parents will surely be grave. Those who are motivated by greed and not wanting to bother caring for their parents need to repent. It is too easy to disguise as "mercy" hidden agendas that are selfish.
I would also add that there is great encouragement in the fact that for true believers death is not the end of a relationship, but only an interruption.
Our loved ones, as they age and weaken, have not passed their peak, as the world imagines. They have yet to reach their peak. And if a peak is ever reached in the next world (I doubt it will be), there will never be a subsequent decline. The thrill of being in the presence of Christ will never wear off, and the adventures ahead of us will always be better than the ones behind. Our God offers not the end of longing, but the continual fulfillment of it—infinite joy and gratitude to the One who did it all for us. Our believing loved ones, whether parents or children or spouses or friends, will be there to greet us, likely eager to show us some favorite places. For those who know the grace of Jesus, the ultimate reunion awaits us.