How long have Edgar Allan Poe's writings remained in common use? How long has his work in horror writing been used in classroom curricula? Is #1 or #2 less than a decade?
Horror fiction
Edgar Allan Poe's writing has endured for over 150 years.  Edgar Allan Poe's horror writing has been included in classroom curriculum for decades.  
genre of fiction
Is Edgar Allan Poe obscure in the world of horror fiction?