Actually, I agree with OP.
I have 4 builder sitting doing nothing, and I feel so painful.
They have been sitting doing nothing for a month or so. And they will be for anther 3 weeks.
Luckily, my lab is still running. By the time my King reach 30, my lab will be done, and my TH will be TH10 at the precise moment. And yes, my lava wall would be done, or ALMOST done at that time.
So... I don't waste any research time.
As he said, if your lab is empty, you're doing it wrong. You didn't raid fast enough
Edit: or you didn't upgrade your wall right. Let the wall at the end is terrible idea. I upgrade my wall along with my defense. When ever I upgrade my defense, I dump all the resources to wall. I only left what's need to upgrade that defense. That way, I save builder time
I also didn't upgrade my collectors and mines until I max TH9. I know that I would finish defense before wall, even if I try to upgrade wall as much as possible, so I playing catch up with collectors, barracks and dark barracks. Yeah, I don't even get hogs until I max TH9)






