Congrats on your 1st successful brisket, they will only get better from here!
In my MES at a steady 275F and unwrapped the whole time, I find about 1hr and 7-10min per pound is usually the area that it can be tender and done. I only pull when it is tender, never by time or temp.
Then add +4 hours to the overall time estimate for rest.
So time per pound + 4 hours = number of hours you want to START with the brisket in the smoker BEFORE you plan to eat.
So if I have an 8 pound brisket (entirely too small btw lol) I estimate about 10 hours or more then +4 hours for 14 total hours.
If I want to eat at Noon then I start it at 10pm the night before.
If it finishes in 10 hours, I have 4 hours to rest it.
If it takes more than 10 hours, I have 4 hours extra time for it to finish and to rest it before eatin time!
Plan like this and you will never have an issue.
If it wanted to fall apart then I think you had 2 issues. 1 - the serrated knife can tear it up a good bit. 2 - if it is still too hot when slicing then it will come apart more easily.
A good 4-5 hour rest fixes that.
One final bit of info that I failed to mention before. Put the meat probe in the tickest yet center-most portion of the FLAT muscle. Never the point, it will lie to you. The flat is the last to go tender so you want the probe in that spot that gets tender last.
Also, I've I use 3 probes aiming for that spot from a few different angles and I go off the probe that reads the lowest.
It is amazingly easy to miss the target spot, so 3 probes and going off the lowest has been my foolproof approach.
I have done tons of brisket smokes and done so many tests on this that I am 100% convinced that people missing the sweet spot with the probe is biggest factor in people reporting "a brisket is done anywhere from 200-212F". Yes there can be some variation due to the meat and quality but the biggest difference I have found is the probe placement. If you ever try it you will know what I mean when 1 or 2 of the 3 are reading wildly higher and the one reading the lowest still probes NOT tender until temp raises and it finally becomes tender there :D
Congrats and I look forward to hearing about your next smoke :D
