The general assumption or belief is that volatility is mean reversing and that selling options on high IV rank are more expensive and are profitable because volatility will decrease and likewise the option price, allowing you to profit on the spread. Is it possible that IV rank or percentile exceed the 100th percentile and stay high infinitely? Why is it assumed that volatility is mean reversing? Isn't it possible for a stock to stay highly volatile over extended periods and increase in vol, thereby putting its average vol on an ever increasing slope?