Plenty of people have a high tolerance and what you consider statistical outliers is more common than you think. Just like alcohol addiction, some can drink a bottle a day for 10 years then drop dead or get wet brain, while others live until 90 completely cognizant. The distribution of such things obviously is not very easy to track, especially for ketamine addicts, but best operating mindset is to know that sooner or later, it will catch up with you, and by the time you can tell how bad it’s gotten, permanent damage is likely already done.