What amazes me about Nathan Myhrvold is that he has 850 patents to his name. How is that even possible? He is 61 years old, and lets say he was working for 40 y

What amazes me about Nathan Myhrvold is that he has 850 patents to his name. How is that even possible? He is 61 years old, and lets say he was working for 40 years. That a more than 21 patent a year, how much he needs to pay for keeping the patent rights each month? I guess after 25 years patent expire but still ...