Sentence:  Though they obviously realized that these episodes were part of something wonderful and important and <WSD>lasting</WSD>, the writers and producers couldn't have imagined that 20 years later “Treehouse Of Horror” wouldn't just survive; it'd thrive as one of the most talked-about and watched episodes of every season of The Simpsons. 
Meaning of the word marked with <WSD> tags:  Persisting for an extended period of time.