The "use before" date on most prescriptions means the chemical has the potential to degrade after a certain point- in most cases, it's still very active for a very very long time. It's rare that age will change a chemical into something that would give different effects, or no effects at all.
Expiration dates are something that legally have to be on drugs to be sold. Any prescription drug fan can tell you, a 5 year old bottle of oxycodone is still a find.
There was a regular poster on here over a year ago who was doing construction in a house that had not been entered since the 80's, and found some pills that were crumbled to bits in the attic- barely even recognizable color. He reagent tested it, and it went positive for MDxx. He did a trip report later and apparently rolled harder than he ever has. These were pills that were likely made back when MDMA was legal mind you, but they were over 20 years old.
MDMA is not made by "kitchen chemists", if someone claims to be manufacturing MDMA easily in their home, they're lying to you.