Game design often involves subtle questions of balance which will only be revealed by repeated play of the game.
Although as many of the game parameters as possible are checked, there is plenty of room for subtle loopholes. You should think carefully about the consequences of each parameter, being particularly sensitive to degenerate winning strategies. Most common are units that are too powerful, too fast, or are built so quickly that they overwhelm any opposition. Players should always be a little "hungry"; not able to get quite as many units or as much material as they would really like.