I agree faye. There should only be a minor adjustment or two at most. Set the off side where it will end, and then girth up to snug. You don't have to crank it, but snug it, and then after you are finished with bridling, or other checks, go back and snug up the girth one final time to make sure it's right. You will end up with a horse that fidgets more if you flit back and forth toying with the girth, than if you just do it up politely and be done.
"Keep a leg on each side and your mind in the middle"