I don't believe that for a second. Your many incarnations are not lived sequentially, as there is no time. Time is a man-made concept and does not exist for the soul. All lives happen at the same time and affect each other in many ways. Every bit of growth and progress you achieve in this life affects your other lives in the form of intuition and hunches and innate talent, and they the same for you. Each incarnation and time of birth was specifically chosen so that you would have the experiences you do, when you do, with the people you have them with. The moon will be at whatever location it needs to be for that to come about in this life, whether new, full, or somewhere in-between.
There are no "last" incarnations as they are all the last one, and the first one. The depth of growth and experience is modified by the circumstances of your existence, the culture you are born in, the class and standing, and the experiences you have. A modern day human living in New York City is no more or less spiritually advanced than some monk living on a mountaintop with no running water. Whether the man-made year is 500 BC or 2014 AD is irrelevant to spiritual growth.
How can you tell the age of your soul? One is by your own inherent thoughts and beliefs, how quickly you assimilate new teachings, how well you can think them through, incorporate them and use them to teach others. Someone who has done this in many lives will get better and better at it just like any other talent. And the more you do this in one life, the more you benefit their lives. The "NOW" continually shapes, modifies and adapts. Your soul may choose to focus on this life, or one in 1472, as the need may be. It may focus on many of them at the same time when a specific theme is being explored. Your own spiritual intuition, dreams and innate knowledge will let you know how far down the path you are. Your hands will give you a clue as the more lines on your hands, the more experiences and teachings you have assimilated, but only those relevant to this life. The natal chart is just the blueprint for THIS life - not the hundreds or thousands of others that you already have.