Potting Soil does eventually go bad in the bag after around 6 months.
You can still use the potty soil to plant things with but the potting soil won't be as nutritious as it was when fresh and may not help the plants grow like it would when fresh.
Still the old potting soil can be used and you could mix some fresh potting soil in with the oil potting soil to help it grow the plants.
Or just add some fertilizer to the old potting soil so that the plants will grow.