That's a cute development choice. -.-
Larian basically gave us the coolest sandbox ever, but by 7:59 PM we get notified we can only play on it until 8:00 PM, right after being teased about how cool things might get by 9:00 PM. Suffice to say I am not particularly happy with this. Who cares, though, right?
Still, I really hope this changes in a future patch. Post-endgame gameplay is a must for sandbox RPGs.