Pills lose their effectiveness over time. Hence, if you take expired pills, you will need additional pills to fall asleep. And consuming a high dose can be hazardous for your health. So, it is safe to replace them after they expire. It is not just about sleeping pills, all medications have an expiration date, and they should be taken according to that only. Expired medication can be harmful or less effective for you depending upon the chemical composition. So, it is best to go for non-expired medicines.