Well I wouldn't be to hasty.
Prophets only speak prophetically as the Lord gives them the words to speak. The Lord was not speaking to Saul either in a dream or by means of urim or prophets.
It would be most strange if Samuel was either able or disposed to go against the Lord's wishes and prophesy. spilling the beans on what the Lord had decreed.
Then there is the matter of timing. Saul was told that the next day, he and his sons would be with Samuel where ever it was that Samuel was resting. Well maybe they were and maybe they were not.
Endor looks to be about 20 miles NNE of Gilboa where Saul's army was camped.
We are told that Saul left Endor by night to meet up with his army.
It seems highly unlikely that they would or could travel far by night in those days, so it would have been much later in the day when they met up with the Israelite army at Gilboa.
So, it was some time later possibly the day after that the two armies met on Mount Gilboa resulting in Saul's defeat and death.
Mount Gilboa would slow any army down considering the weight of armament and food and water.
It is quite believable that what posed as Samual was in fact a lying spirit that only told Saul partial truth. That the spirit would know what was to happen and why is not surprising, and I'm wondering if Saul was fed some unrecorded lies that would make him leave in the night....why would he do that believing that he would die next day in battle?...unless he wanted to warn his sons.
So why would Satan send in a lying spirit? If many people are deceived into believing in mediums and so on and can be fooled into thinking they can be put into contact with some much loved departed relative,.......so much the better from its point of view.
Another troubling detail is that Saul was shown or told the visitor was an old man dressed in a robe...just what he would have expected Samuel to be looking like.
So in summary, the late Samuel would not be able to prophesy if for no other reason that we are told already that the Lord did not speak to Saul by prophets or any other means.
The distances involved especially for people probably carrying supplies and arms would most likely involve more that one day to travel...from Edor back to Gilboa, then on back up Mount Gilboa.
Scripture does not seem to confirm that Saul died the next day, it is just something hat would be assumed if Samual did indeed come up to preak.
The Lord does not ever go back on His word, and no medium has the power to over rule the Lord's will.
So that is my thinking, you and others might see these things another way.
