What does Daniel 6:28 mean?

Chapter 6 concludes by noting how Daniel experienced continued success during the reigns of Darius and Cyrus. Scholars debate the exact identity of the "Darius the Mede" mentioned in this story (Daniel 5:31). According to the traditional timeline, Daniel would have been nearing ninety years old when he survived a night among lions (Daniel 6:19–23). He would live until shortly into the reign of Cyrus, delivering important prophecy in those final years.

The day Daniel was cast into the lions' den was dark and foreboding, but God turned the darkness into bright light by rescuing Daniel and turning the tables on his jealous enemies. God continued to bless Daniel to the end of Darius's reign. According to some identifications of this Darius, that reign lasted two years. Daniel also prospered in the reign of Cyrus. It cannot be determined how long into the reign of Cyrus Daniel lived. By that time, he was very old, but he was still alive in the third year of Cyrus's reign (Daniel 10:1). God sometimes grants longevity to his servants. The apostle John is said to have been in his nineties when he wrote the book of Revelation. One thing is certain, the believer's years, whether brief or long, should be lived to God's glory.

It has been observed that God's servant is immortal until his life's work is done. This is not an excuse for carelessness, but a reminder that God, not man, is in ultimate control of our fate.