That would be some 36 years to make the loop with the 18th and 19th years the most intense. That would include lots of younger folks seeing it every day, if the sky is clear enough, for most of their lives. The math is too heavy for me;)
Anyway, it hasn't made it close enough to see by common telescope yet, so it is at least quite far away. About a million people are watching for it so we can expect it to be spotted, perhaps as it passes through the orbit of Pluto, or closer. The 2012 thing may hold a clue. Could be the onset.
Going to be interesting to watch how things proress.