I'm pretty sure that under correct storage conditions (usually a dry, dark, sealed container) pills work long after their expiration date. I'm pretty sure that pills can last at least 15 years, and my experience was with pills that was 30-40 years old, although they were military grade IDK if there is a difference.
I've taken military "go pills" AKA methylphenidate that was from the 60s or 70s
OD--> BDD