|One last question, do you think it would be worthwhile to conquer all but one planet of the galaxy|
That's called milking the game and is a bit cheesy at least, not to say that it isn't done on occasion.
From what I've heard, it can help but it's only worthwhile if you still have significant growth in at least a couple of categories. Even then it gets to diminishing returns very quickly. If you still have a lot of pop to grow or if you haven't finished building out your planets then it's probably worth it in points.
It's hard not to do this to some extent but what I mostly do is allow myself to finish out the year that I'm in when I get to the point that can immediately win. I try to end the game right on Dec 22nd. Some people would consider even this cheese, but I don't find it unreasonable. Much beyond this I would consider cheese, plus it really doesn't get you that much. If you want to hit the turn button for another year for 5K in points, then knock yourself out.
What you can do that isn't cheese is to plan your strategy to maximize points long term over the course of the game. This is not only not cheese, it's far more effective at getting a high score.
As I mentioned before, the score seems based on the area under the aforementioned curves (the integral). So if you play the game without regard for score and get to the point that you’re about to win and then start doing things to increase your score while milking the game, this really only results in high values in the appropriate curve right at the very end of the game. If instead you base your strategy around getting large values in the appropriate curve as early as possible, not only does it build a bigger score, it actually helps you win.