Fallout 4 serves up a hefty chunk of the Wasteland for you to get thoroughly lost in.
Apparently, it takes 11 minutes to run right across Fallout 4's game map.
Some commenters have suggested that this isn't long enough. If this gives you worries about Fallout 4's longevity, I recommend loading up Skyrim and timing yourself running across the map via the most direct possible route to see how long that takes.
Then stop to consider: how many hundreds of hours have you sunk into Bethesda's last game...? It's not raw size - it really is what you do with it.
Fallout 4 launches on PC, PS4 and Xbox One on November 10. If you've played both Fallout 3 and Skyrim, you know what you're probably getting into. Take a week off work.