Brisket Advise

Need some advise on the brisket cooks. I have only cooked about 10 in my BBQ life so learning all the time. I have tried hot & fast and also 225 deg. I have used my Shirley and also LSG IVC. I always tried hot & fast with my Shirley because I had to continue feeding sticks and baby sit the cook. Now that I am cooking on the LSG IVC I usually cook through the night as it holds temps incredibly well and allows us to eat dinner at a normal time without me starting real early or through the night.
My question is in regards to finish temperature or probe tender. I totally get the probe tender and my briskets have been awesome. Very happy with how they are turning out but wondering if they can be better. What I am seeing is my briskets get to about 196-198 and they probe like butter. I consider them done. But the last 2 cooks I let them go to see if they get even better. I am seeing my temps drop to around 180-190 even after an additional 2-3 hours. I also don't think they get better by the probe like butter method.
Am just not letting them go long enough? If I am cooking at 225 degree will they never get to 203 degree internally? Should I quit worrying about the internal temp of the meat? They cut fantastic, have a nice bark and pass the pull test perfectly.

thanks for the feedback guys.