There are three major reasons for an electrolytic capacitor to fail:
1. The electrolyte dries out
2. The oxidation on the metal plates wears out on stock
3. Exceeding working conditions somehow destroys the oxidation

Every electrolytic capacitor dries out eventually. This will happen also to those russian capacitors which have glass sealings and stainless steel outer mantle. The process will be slower on those but it will happen.
The electrolyte inside the capacitor is not liquid. It is more like hair-gel which is used to moisture the insulator (paper) between the rolled metal plates. Although the sealing in cheap capacitors is "leaky" the gel will not evaporate easily. If the capacitor has dried out it will not exploce or anything like that. It is just like an open circuit.

If the capacitors are stored for a very long time the oxidation will become thinner. I have met this phenomenon when restauring ole tube radios. If those have been sitting on attic the capacitor is more like a short than a capacitor. It can be brought back to operating condition by applying a weak current on it. I usually put a 100Kohm resistor in series with the rectifier (tube) and let it simmer for two days before applying the full power to the system. This way the oxidation builds itself back.

Quickest way to destroy an electrolytic capacitor is to reverse the poles and apply full working voltage to it. It will exploce in not time causing a lot of hairy stuff fly around. The smell is also unmistakable. I have met a few capacitors that have had their markings the wrong way....