So i don't knwo about anyone else but I prefer to use two constant characters all the time and have another switchable character. In my case I always use Squall, Irvine, and Rinoa. But in the cases where you can't use Rinoa, like the whole 3rd disc for exampe, I choose to use selphie. And yes I know that there are times where you can't use any of thes characters, but then you just junction the crap out of them and make them as tough as your other characters.