Bought a brisket in Spring but never did smoke it. Will be 51 degrees tomorrow. Might have to smoke it for 5-6 hours and then finish it in a 225 degree oven wrapped in foil, same as would be done on the smoker. Makes for a long day of cooking 12-14 hours so sometimes I do the big cuts by starting on the smoker in the afternoon, early eve and finishing in the oven overnight.
If I keep it until Spring, it might be ruined and a whole brisket ain’t cheap.
That is how I would do it too.