[Leigh B]

Electrolytic capacitor is made of thin aluminum foil and wet paper. It's not sealed completely either.

There is no paper in an electrolytic capacitor. The electrolyte is a very thin layer, like a film.

They are completely sealed. That's why they have a pressure-relief plug or can scoring.
That's also why they explode when they fail.

The manufacturers recommend that the caps be re-formed (see post #3) if they've not been powered up for six months.

Novatron recommends operating their packs at least 30 minutes every four weeks.
They recommend re-forming the capacitors if the pack has sat unused for longer periods.

- Leigh