Electrolytic "wet" capacitors (Aluminium Electrolytic Capacitors) can survive decades without noteworthy losses in capacitance or increase in ESR, but only when powered on regularily.
Examples are many old HP or Fluke equipment, up to 40 years old.
If stocked only, the Al2O3 dielectric layer will degrade by the wet electrolytic inside.
The capacitors then won't withstand the rated voltage any more, and will draw a big, maybe destructive current when being powered with full voltage, after years of storage.
For that reason, after about 7 years, spare part capacitors (these wet electrolytic ones) will be scrapped in our electronic manufacturing plants.
You may "reform" this dielectric by carefully charging the capacitor with a current limited voltage in first instance, say a few milliamps constant current, compliance voltage should be set to nominal voltage. Then the decrease of the residual current should be monitored. It will reach after some prolonged time, the specified current leakage current of several µA, again.
Frank