How well can you defend?
If you hold a planet for a long time can will it increase it's defenses? LIke in space it will have more space stations, and on the ground the defender's base will get better. Like it's walls will increase in size and it will have more turrets and stuff. If you hold a planet for a really long time it will turn into Troy, only beatable by one of the biggest armies ever and a wooden hollow pony.