I've cooked a great deal of brisket, and after experimenting cooking to different internal temperatures I have come to the conclusion that 180-185 is a bit low for me.
For a long time I did use the 180-185 target and it's cooked and tender enough to pass, but still not quite where I want it to be.
I now go 190-195. On my last cook I did two briskets of identical weight. I pulled one off as soon as it hit 193. I left the second one on while I cut up the first and did a bunch of other things. The temp was starting to moderate in the cooker by this time anyway.
I didn't pull the second until maybe two+ hours later. It was too tender to slice and basically became chopped while trying to slice it.
The internal temp on #2 was also 193, which hadn't moved in the two+ hours it had been left on since the first one was pulled.
So, it seems to me that it's not only a specific internal temperature, but also how long it's been at that internal temperature. With the slow temperature changes in these large cuts of meat it can make a difference.