Up to the present, all known lifeforms have had lifespans which are extremely short relative to the ages of stars and planets. This applies fully to the human species for which there is no authenticated record of any member living for more than 123 years. If you wish to achieve a substantial increase in your potential for happiness beyond that of your forbearers, then you must perforce live well beyond age 122. Yet, while there are some methods which may increase your lifespan very moderately, and we even appear to be on the edge of major scientific advances that will increase human maximum lifespan, there is currently a major (and likely always will be some) chance that the material substrate which supports your mind will sufficiently decay that the mind is either partially or fully lost. In fact, we define the "death of the individual", information theoretically, as the irreversible loss of the information contained in the individual's mind.
In this section, we present information on the theory and practice of current efforts aimed at the damage-free capture of the information which is thought to be sufficient to define and, theoretically, to reconstitute a human mind. Since these methods have usually been aimed at preserving human bodies and minds together, they are generally known by the name suspended animation. Currently research to perfect human suspended animation has recently progressed sufficiently far that if a relatively modest research effort was consistently persued, its ultimate goal (low-risk, long-term human preservation) could be achieved within 10-15 years.
For information on additional applications of long-term perfected suspended animation examine the pages of the The Life Preservation and Continuation Society
That which makes each human unique, in personality, memories, intelligence and other mind attributes is information, ie. the structures and organization of the brain, not the matter of the brain.
It is possible to conceive of preserving the information of the brain without preserving the matter of the brain or even contemplating the restoration of that matter to previous functionality. If this is done then the unique person has still been preserved and might possibly live again in another human body or some other material substrate.
Since modern neuroscience does not know definitively in what brain structures the unique identity information resides, science cannot say definitely at this time that any preservative procedure is, or is not preserving the essential and unique identity information. Therefore, if you want to continue living, and if you have sufficient funds that removal of them from your assets to purchase cryopreservation (currently the only method with any objective chance to succeed) does not decrease your life happiness beyond the potential of the happiness to be gained multiplied by the chance of success, it makes logical sense to be cryopreserved even with the poorest of today's cryonics methods rather than to have your unique identity information clearly and irreversibly destroyed by traditional methods of processing the deceased.
My own assessment of the chance of full restoration of the identity information in my own body with the technology of a few years ago was about 1 in 10,000. However, such major research advances have occurred in the last 5 years, that I now put the chance of full restoration with the current best possible cryopreservation methods at 1 in 100. Unfortunately, the current best possible cryopreservation methods are still not fully implemented and available from any practicing cryopreservation organization. Thus, the major problem today is that the "best possible cryopreservation" is not obtainable because the cryopreservation organizations are too small, and, in addition, they are too narrowly located to respond sufficiently quickly to any sudden or remote death situation. Another major problem is that cryopreservation cannot legally begin until medical declaration of death. While biologically this arbitrary (legal) definition of death does not necessarily mean that life cannot begin again, the time delay which is incurred means that much damage to the brain can occur (eg. Alzheimer's disease).
Given sufficient funding and consistent direction, research starting with current technology could culminate in the perfection of suspended animation within 10-15 years, and its establishment as an elective premortem medical procedure within 25 years. For an outline of how this would be accomplished see the Internet achived pages of the Prometheus Project. The only research organization currently capable of successfully pursuing such a project is 21st Century Medicine.
Any cryobiologist who says categorically that cryonics won't work is to that extent no longer being a scientist. Any objective scientist must agree from the above logic alone that there is some chance of restoration. He may estimate it to be much lower than I do, but he cannot scientifically declare that the chance is zero, and therefore, while he may legitimately cry out buyer beware!, he must respect the reasoning and the rights of those who elect cryopreservation to make that choice for themselves.