Oh, I did that with my first butt.
I'm trying new methods. I could have easily gone another couple of hours with the remainder of the butt and I'm pretty sure that it would have rendered all of the fat out. I still would have been something like an hour or two ahead of the time it took for the other butt (I think I went something like 13 hours and ended up at 205.) I actually let the other part of this butt go another hour in the oven and stopped at 185. I think that at 9 hours, I probably would have only had another hour or so before it hit 205, and I'm pretty sure it would have ended up the same as the one that I went low and slow for the whole time period. When I pulled the first piece off, it was very tender - I just hadn't rendered all of the fat.
I actually liked the way the fat worked with what I pulled early. Even when I pulled the remainder and threw it in bags, it was pretty close to having the fat completely rendered.
I microwaved a packet of the remainer today (about 3/4 of a pound) and it came out tasting very good with not so much fat as the first part I pulled early. There was still a little bit more of the fat than I had with my first butt, but had I chopped it up, it would have pretty much disappeared into the pork. It DID melt in my mouth, along with the remainder of the pork.
I think my point is that the first piece I pulled was at a lower temperature than what others have reported as "pullable". This piece pulled just fine and was a little different in flavor and texture than pulled pork is. The next time you do a low and slow butt, try pulling off the end of the butt a little early and try it. If you don't like it, it's pretty easy to put it back on and finish it off normally. Yeah, I know that you've just opened it up to losing some of the moisture, but I can tell you that the remainder of the butt was very moist when I pulled it at 185, even having the butt torn open on the end. No problems there. Flies a bit in the face of conventional wisdom I know. I'm just reporting what I found. Actually, it's a good thing that it turned out that way because, I don't know about you, but I get really hungry around the 8 hour mark, with all of those great smells...
Also, keep in mind that I didn't crank up the heat at the end, the heat was naturally higher than normal at the beginning of the process. If you track my comments, you'll see that for the first 4 hours or so, there was no way to get the temp low under the Weber's hood the way I set it up. It HAD to be 300 degrees or higher at first. I'm thinking that the "low and slow" part really comes into play after the butt hits 140 and above. Could be wrong though. As long as you aren't trying to cook it at 400 degrees for the first 4 hours, I think that you're fine.
Sorry for being so verbose. Just trying to work through the process...
PS, I think that you can still consider the process that this butt went through "low and slow" if you take into account all of the temp variations and the amount of time to cook 7 lbs of meat. No, it's not 12 hours plus, that's for sure.
Thanks for the comment.
PPS, the only "waste" (not edible) I've had so far is one peanut sized piece of fat/gristle. I still have almost 2 lbs in the freezer though...however, if you can't abide any actual fat, even if it melts in your mouth, you might have a different impression.