I'm still on chapter 12, but I've got an A on every missions, every skirmishes.
I already got the hang on the game. Now, it usually only take me a 2nd pass at the battle to get an A, getting the Aces and everything in the process.
I enjoy it much more like that, as getting an A is fitting perfectly with how I play SRPG: perfecting my tactics and strategies.
I'm also detailing everything I do in a kind of guide, and the scores I get. I'm pretty confident I'm getting the best possible scores. Very satisfying. Also, I'm doing the skirmishes only once, so I'm not over leveled.
Usually, my units are a bit under the level of the chapter I'm in, though they are slowly gaining on that.