When have we ever conceived of a specific technology, which we had any understanding of the workings behind, and taken hundreds of years to make it?

http://www.alcor.org/cases.html - 1967, first human cryopreservation. That was 45 years ago. We've already been nearly half a century, and I haven't seen any research that suggests that revivification is likely to occur in the next decade. Calling it a century from the first human cryopreservation, a mere doubling of the time we've already waited, does not seem at all like an unreasonable assertion.