In "The Neutral Zone", Dr. Crusher argued that people in the 24th century didn't mind dying. The 1990s attempt to prolong life through cryogenics that was described in the episode was considered bizarre, and Crusher only went through the trouble of reanimating the dead bodies because the issue was one of historical-scientific curiosity (and, she incorrectly assumed, an order from her CO).
"Unnatural Selection" showed that transporters can take a few days off one's aging process, although it left things slightly vague on the issue of whether that also erased the memories from those last few days. I vastly prefer to interpret the scenes so that the erasure did happen, even though this clearly wasn't the writer intention. This alone would negate the usefulness of that technique in actually prolonging life; if not, later episodes would establish that transporter patterns do not survive for long, eliminating the original plan of our heroes (but still unfortunately leaving the actually utilized Plan B where the pattern was divined from a hair follicle, a scientifically unsustainable idea).
So in general, I'd argue that life can be prolonged and death reversed, with effort - but the effort still remains considerable, is only possible at top-end facilities (and the sickbay of the top-rate starship might be more advanced than the best hospitals, really), and generally isn't considered worth the fuss.
But who knows, perhaps a few eccentrics do elect to live for thousands of years? Ira Graves did seem to attempt this, in a certain specific way that would bring him professional fame. It just doesn't seem to be all that popular a choice.
Timo Saloniemi
