Leon Denis, in his book, Life and Destiny, reports on what he has detected, in conversation with spirits, are the spans of time experienced by spirits between one physical life and the next. He shares with us what he has heard;
“According to some theosophists the return of the soul to flesh is effected usually each fifteen hundred years. But our own testimony, gained from great spirits does not confirm this. Interrogated in great number and from various centers, they reply that reincarnation is much more rapid than that. The souls eager for progress dwell a brief time in space; they demand a return to this world to acquire new merits. We possess information regarding past lives of certain persons, gathered from the lips of mediums who know nothing of these people, yet which was in perfect accordance with the facts and intuitions of the interested parties. These statements indicated that ten, twenty, thirty years only separated the terrestrial lives of some individuals, but there was no precise rule. The incarnations were separated widely or followed closely, according to the state of the souls, their desire for work and advancement, and the favorable occasions offered them. In the case of premature death reincarnation was often immediate.” [Life and Destiny, Leon Denis, p. 151]
What Leon has described coincides with what I have read in Andre Luiz’s books. Spirits who are dedicated to improving themselves do request to return to physical life within a decent time period. On the other hand there are spirits who have wandered the earth for hundreds of years, seemingly stuck in place for a very long time. Although, eventually they will awaken to the call of a better life.
In the book, Memoirs of a Suicide, Camilo Castelo Branco, stayed in his celestial colony for a considerable time longer than the others in his group who also killed themselves. While they spent the range reported by Leon Denis, ten to thirty years being rehabilitated and then jumping back into their physical trials, Camilo, dreading the required difficulty of his next life, spent longer in the spirit world.
Therefore, independently of Leon Denis’ observations, I believe he is correct; first, there is no set time, as in the physical world, everyone is different. But, for those who are actively pursuing their path of improvement, the pace of returning to earth is more regular.
For those who wish to learn more about the Spirit realm and what is it like to live there and what are the different levels, I have a book which explains why you are on earth and what happens to you in the spirit world, please read, Explore Your Destiny – Since Your Life’s Path is (mostly) Predetermined.