Yes indeed. Also, the builders are likely to go off and build the small hut and/or repair the loveshack. If both those jobs are completed they'll mill around aimlessly until you open the game and give them something to do. I don't need either hut at this stage, so I prefer to switch the builders to research immediately they've finished the dam.

In fact, wherever possible, I try to guess when a building task will be completed and make sure the game is open. It's not always possible, alas (there's an annoying period called working that I have to spend away from the village).