I use combat trim for every plane and every sortie. The Trim going out of balance just gets tiring to fix. I'm sure there are some advantages to taking it off, but for the most part, it doesn't make life changing differences. In turn fights, if your plane is out of Trim, by using manual Trim, it can make your plane actually turn worse, and make shooting harder, if you don't know exactly what you are doing. If you are just getting started in the game, or aren't very experienced in the game. I'd leave it on all the time, so that you can learn how the plane feels at first. Sometimes I think beginners who tweak Trim, actually do themselves a disfavor, rather than making them turn a tiny or slightly bit better.