All of LDW's realtime games are designed to keep going, even when you're not actively playing the game. Some people do pause the game so that they don't "miss anything" while they're away, although progress in the game will be slower that way.

Depending on how long you plan to be away from the game, you might want to adjust the game speed so that your village doesn't suffer from neglect. You don't have to return to the game menu after exiting to do that, though. You can set the game speed while you're still in the game and then exit. The speed setting takes effect as soon as you click OK on the preferences screen.