I will do that, too. I wonder how long baking powder does last since I have several bags of SR flour and meal.
I can’t remembered where I borrowed this.
Baking Powder = 1 tsp. baking soda + 2 tsp. cream of tartar
While you may not think of storing cream of tartar, this actually makes a lot of sense. Both baking soda and cream of tartar can have an indefinite shelf life if stored in airtight containers at room temperature. Baking powder, however has a short shelf life of 6-12 months. To test if your baking powder is still active, stir 1 teaspoon into ½ a cup of hot water. If it doesn’t bubble, it will need to be replaced.