The matter of longevity in the Caucasus region has been investigated thoroughly. It turned out that people living there tend to add years to their real age, since the older they are, the more respect they get in the society. Regarding that elder who allegedly lived up to 168 years old, you should remember that the Caucasus region had been an arena of ferocious warfare through the whole 19th century (and well into the 20th), so I doubt that there can be reliable sources of census data that old...
The case of the 168-year old guy seems to be very unreliable, and your argument might be one of the reasons why so many people from the Caucasus claim that they are super-centenarians. That said, these stories continue to pour in from the region. One of the examples is here:
http://rt.com/news/oldest-man-labazanov-dies-dagestan-902/And also, the Caucasus republic of Daghestan is having the highest life expectancy in all of Russia, at 75.6 years.