Hey Bob, good to see you around here again! I'd say "congrats" to your briskie successes!
As far as the timing goes:
1. All meat is different... Go by IT and don't sweat the time.
2. It may have something to do with your supplier. Typically, they get meat from the same producers, so the quality of the meat is consistent. Like your briskets, I have similar results with pork butts. The ones I get at my local Sam's Club
rarely take more than 1 hour per pound, which is also contrary to most postings on here. I'm OK with that.
Meat is made by animals, and no two are the same.
3. If concerned about meat timing, see step 1 above.