How can divine justice be reconciled with a man who died at an early age (25 years) having many good deeds, and another who died at an old age (50 years) having more good deeds due to his longer life?

What God grants His servant in terms of rectitude, longevity, and good deeds is purely His grace. And if He punishes the wrongdoer, that is His justice. Allah is not questioned about what He does due to His perfect justice and wisdom, for everything is in His dominion and grasp. Allah bestows His grace upon whomever He wills, and there is no injustice to anyone who is not given like others, for servants do not enter Paradise by their deeds, but by Allah's mercy. And their acts of obedience cannot counteract Allah's blessings upon them. If He were to punish the inhabitants of His heavens and His earth, He would not be unjust to them. Thus, Allah's grace is boundless, and He has the ultimate argument over His creation.