The problem with this situation is that if it's a busy weekend day, I'm not letting anyone play through. Two weeks ago I played on a gorgeous Friday afternoon, and there was an hour and a half wait on the first tee. I was paired with 2 higher handicappers and one a little better than myself. Somehow a twosome was behind us, and they rode us the entire round. On the 7th green one of them hit into us (not sure if it was intentional). One of the high handicappers asked if we should let them play through. I said not a chance in hell. If we let them through, they will just be waiting on the million groups ahead of us, and then we are expected to let everyone that is right on us through. We offered to let them play with us to slow them down, but they didn't want that. So they stayed behind us.
Point is sometimes you're just going to have to live with a 6 hour round. Yea it's no fun when it happens, but life isn't always fun is it?