JOEL - Both ancient and modern prophets foretold that, at the end of a thousand years of peace, Satan would be loosed, sin be introduced back into the world, and the final battle between good and evil would be waged (Rev. 20:7-8; D&C 43:31).

Orson Pratt has said concerning this:

"When the period called the Millennium has passed away, Satan will again be loosed. Now the query arises, Will Satan have power to deceive those who have lived on the earth, and have fallen asleep for a moment, and have received their immortal bodies? No, he will not. When they have passed through their probation, and have received their immortal bodies, Satan will have no power over them. Thus generation after generation will pass away, during the Millennium, but by and by, at the close of that period, unnumbered millions of the posterity of those who lived during the Millennium will be scattered in the four quarters of the earth, and Satan will be loosed, and will go forth and tempt them," (Journal of Discourses 16:322.)

So the ones who will be tempted are those generations of children remaining at the end of the millennium who have not yet received their immortal bodies.
All children who die before the age of accountability will never be tempted.(Joseph Fielding Smith, Doctrines of Salvation, 2:56-57.)

RICHARD - I am trying to understand what Orson Pratt is saying: My question is:
How could you call time on earth during the mellenium a probation period when you have not been tested and tried.e.g If a child is born to mortal parents during the mellenium then dies as an adult or as an elderly person,then changed in the twinkling of an eye and this type of person has never been tested & tried by satan. A person born for example as a matter of speaking Jan 2006.The commencement of the mellenium started Jan 2005. This same person grows old and dies at age 90yrs old Jan 2105 and changed in a twinkling of an eye. How can this scenario be a probational period?

JOEL - From what I have read I am quite certain that once a person has become immortal, they can no longer be tempted by Satan.
President Joseph Fielding Smith said:

"Satan will be loosed to gather Its forces after the millennium. The people who will be tempted, will be people living on this earth, and they will have every opportunity to accept the gospel or reject it. Satan will have nothing to do whatever with little children, or grown people who have received their resurrection. (Doctrines of Salvation 2:56-57.)

I have thought of the issue you raise as well and have come to the conclusion that these people must be considered a special case, much like infants who die before 8 years old are guaranteed the Celestial kingdom without having to be tempted or tested.
In a Sermon given by Joseph Smith, Jr., March 20, 1842, refering to a young child that had just died he said:

"The Lord takes many away even in infancy that they may escape the envy of man, and the sorrows and evils of this present world--they were too lovely and too pure to live on earth. (The Words of Joseph Smith, pp. 106-109)

I believe people are sent down to earth at appointed times according to God's will and according to what we did in the pre-earth life.
Perhaps those people who are saved to be born and receive their immortal bodies during the Millennium, were also too lovely and pure to come at any other time and like those small children will not need to be tested.