So far I've always managed to complete the objectives for the campaign levels, and I know there are various conditions that trigger a loss (losing an election, coup, having your palace destroyed). But what happens if I just keep playing a level without either of these things happening? Do I eventually run out of time to complete the level and have to start over from the beginning?
There is no time limit. This guy seems to agree with my own testing.
I don't believe that the campaigns have time limits, since I've played one to 2013 before, which is past the limit for any sandbox game.