Don't repeat crap you read on Internet without understanding what are you doing.
Electrolytic capacitors can last for decades, without major degradation.
If you keep them at room temperature, at right voltage, with low ripple current trough them to minimize dissipation etc etc..
All bad elko lore is coming from equipment that runs too hot (valve amps 30 years old, or high density power supplies, or stuff that has problematic engineering) running low quality capacitors. None of that crap exists inside speaker cabinet.
Second part is that speaker crossovers shouldn't use standard electrolytic capacitors. They should be bipolar elkos or some type of block or film capacitors and those don't go bad unless they were damaged otherwise (electrically or mechanical), but in that case speaker drivers are usually damaged too..