What does Revelation 22:2 mean?
The river in New Jerusalem flows down the city's main street. It may divide and flow around the tree of life. Or perhaps a row of trees flanks the river on each side and produce twelve kinds of fruit, a different fruit each month. There is great meaning attached to the use of a tree: this evokes images of the garden of Eden, where God had originally placed mankind and a tree of life.The leaves of this tree possess medicinal properties that benefit the nations. If this depiction includes part of the millennial reign of Christ, then earth's regenerate rulers likely shuttle to New Jerusalem to acquire these leaves and carry them back to earth. That would coordinate with the longevity which characterizes life in the millennium. Isaiah 65:20 indicates that a person who dies at age one hundred during the thousand-year reign is young.
Early in human history longer life spans were the norm (Genesis 5), but the advance of sin in the human race and the curse on mankind reduced the life expectancy. With the curse removed by Christ's victory and sin held in check, food will be nutritious, disease will be infrequent, and longevity will return. In eternity, of course, there will no longer be any death, at all (Revelation 20:14).