Yeah 18 hours is a marathon! What temp were they running at? If it was super low, like 200 degrees, I guess I could see it. But even then that feels extreme. Was it a massive packer cut or something?
Ever tried wrapping in foil after the stall? I had a 16 pound packer that took about that long once, holding at 225 the whole time. The foil helped push through the stall faster, but it still felt like forever. Honestly, the bark gets a bit soft that way, but the meat was still good.