Baking soda and baking powder both have quite a long shelf life. But they won't last forever, and The Kitchn has helpfully offered some simple hacks to figure out whether your baking soda and baking powder are still good:

Baking Powder
Stir 1/4 teaspoon of baking powder into 1/2 cup of very hot water. The soda will immediately start to bubble if it's still good.

Baking Soda
Use the same method, but add 1/4 teaspoon of vinegar to the water before adding the soda. As before, if it bubbles up, your baking soda is still good to use.

Don't see any bubbles? You'll need to buy more. A bit of fizz means there's still some life left in them. Learn more over at The Kitchn.