Don't worry about it. I'm almost positive that having build up means that your lips are still healing. You just don't notice it because you're keeping your lips moisturized. It's going to keep creating a scab until that part of the lip has been fully regrown. Because we're keeping it moisturized, it doesn't have a chance to dry up and peel - causing it to stay on longer and promote more healing.
What's interesting is that when I wake up every morning, I see small pieces of dry skin randomly hanging off, which I clip off. I have a feeling that this is the part of the scab that is truly ready to come off.
Also, there are some parts of my lip that are fully healed where there has been no build up for about a month. Because of this, there are only small areas that have still been building up. But this is hardly noticeable because of the moisture I'm putting on.