I've realized that if my Star Wars: The Old Republic companions had as many abilities as I did, it would needlessly complicate the gameplay. But, for some of my companions, I can't tell if their abilities have changed at all throughout the course of the game. I don't have any character above level 15, so I may have just not seen it yet.
Like the title says, do I have to train my companions like I have to do to gain my abilities, or do I not have to worry about them as they'll gain those abilities on their own.