There are 144 quests in total in the game (and that's not including DLC content). Whatever you choose to do, if it's getting closer to Shaun's locations as soon as possible or just wandering around trying to find a nice weapon that's unique in the game, the game has enough content for you to do before getting to the end of the story. Fallout 4 is a huge open-world game with tons of hours of content for you to play through.
