Most definitly.  So you must find that happy medium on buildup vs time spent.  People who play a sandbox game in a certain way for very large 6-7 digit scores do this.  They will check every so often to see if a win is starting to bring in less points.

They would save the game, win it, check the score, reload the game and continue.  Note, they don't submit the game to the MV when they win it.  They way they have things set up, it's very easy to win, they are just score-building with the AI under their thumb.

The question was clear.  But by playing out the game further in order to build up your military/economy to up your score, there will be a point in which you score will finally start to decline since what you're doing to up the score no longer is offsetting the amount of turns played.

Winning a game in 13 turns yeilds a really nice score for the amount of time invested in the game.  People have knocked out a 100,000+ game before the first year is up by taking advantage of that quick game mentality.  These are just sandbox games, not the tournaments...

So the answer is both yes and no I guess.  Yes, finishing a game that you don't intend to try and score-monger with a mil/econ buildup will yeild you a better score.  However, if you try to eek out every last point per game and are going for the econ/mil buildup idea, then the game will be longer, but there will be a point that it should stop for points.