Too late for usable input on your cook, but for future reference:
I typically always inject pork butt if time permits. I prefer to inject about 8 hours before cooking, but sometimes I have had only 4 hours prior to cooking.
When cooking injected pork butts I find the bone begins to wiggle at about 187° (internal temperature has no bearing on being done).
I always calculate a 3 to 4 hour hold time in an insulated cooler after the cook. This gives me a cooking buffer if the meat takes longer, and pork butt/pork shoulder is one of the meats that benefit from holding in a cooler because as it stays at temperature the connective tissues continue to breakdown into collagen making the meat moist and very tender. The rest period also allows you to get other things ready, or even a rest before your guests arrive.
I find the Brine keeps the pork exceptionally tender, moist, flavorful, and it pulls in very long strands which is great for sandwiches. You'll notice that not only does the pork pull in long strands, but it also keeps it's warm color with plenty of pink from the smoke ring, and it never turns dull gray in color.
In the end you should choose the method that works best for you, not what works for someone else. After all you are cooking it, and only you, your family, and your friends will enjoy the results of the cook.
