Based on the following information it seems reasonable to me that as long as we have all of our original body parts in tact, we should be able to rejuvenate ourselves to a much younger biological state. How ever that is defined. I personally would like for anyone just meeting me to think they are looking at an ideal 25 year old with all systems running optimally and efficiently.
From How Stuff Works: According to researchers, the body replaces itself with a largely new set of cells every seven years to 10 years, and some of our most important parts are revamped even more rapidly.
The body’s cells largely replace themselves every 7 to 10 years. In other words, old cells mostly die and are replaced by new ones during this time span. The cell renewal process happens more quickly in certain parts of the body, but head-to-toe rejuvenation can take up to a decade or so.
Skin: The epidermis sees a fair amount of wear and tear, thanks to its role as the body’s outermost layer of protection. These skin cells rejuvenate every two to four weeks.
Hair: The body’s natural fuzz has a life span of about six years for women and three years for men.
Liver: The liver is the human body’s detoxifier, purifying a wide variety of contaminants from our systems. It’s aided in the process by a constant blood supply and remains largely immune to damage from these toxins by renewing itself with new cells every 150 to 500 days.
Stomach and Intestines: Cells that line the surface of the stomach and intestines have a difficult, short life. Constantly battered by corrosives like stomach acids, they typically last only up to five days.
Bones: Cells in the skeletal system regenerate almost constantly, but the complete process takes a full 10 years. The renewal process slows down as we age, so our bones get thinner.