I've done about 8 butts so far and I usually pull off around 190-200, the foil/coolerize it for about an hour.

The time in depends on the size, temperature...

To be honest, even when I've done a small butt (6#), I've seen it take almost 20 hours. If you take a look at the recipe on BGE's site, it says 20 hours. This is what I'm finding - is that no matter what size it is, for some reason, it takes around 20 hours. Now, you can speed things up slightly by increasing the temp after the 'render' perioud if you want, but that temp is only going to get inside the meat so fast, just because of the meat/tissue, etc.

When measuring, make sure that the probe is AWAY from the bone (if there is one).