Peppermint including peppermint candy does eventually go bad if not stored properly.
Although the peppermint candy will remain safe to consume after expiration date but it may not taste as good and have signs of discoloration and stop giving off the peppermint smell.
Peppermint candy is best eaten within 6 months to a year.
When you have old candy you can freeze the old candy, donate it, bake with the old candy or even eat it.
Candy is still safe to consume even after it is become old and expired and there's no need to throw it out.
Hard candies do not go bad or spoil like other foods will and are safe to eat many years past the expiration date.
While the quality of the candy will change and not be as good it won't make you sick to eat old and expired hard candies.
I've eaten hard candy and other candy that was 10 years old that my Grandma had left in her house when she died.
There was no need to throw it out as it was completely safe to consume.