The original Five Nights at Freddy's takes about two and a half hours to beat, especially when common Five Nights at Freddy's mistakes occur. That being said, the Five Nights at Freddy's titles are very bite-sized, so it is possible to enjoy one, or even all four of the games, on Xbox Game Pass before they leave the service. The spooky month is a perfect time to play horror games, but losing the chance to play those games is certainly disappointing.
Xbox Game Pass is losing many horror games soon, and multiple Five Nights at Freddy's games lead that list.