Speaker Demagnetization?

I have an old 210-sixty-five with stock speakers. I believe they're alnico. I understand that speakers can become demagnetized, and that when they're reconed it's common to remagnetize them as well. Is there any reason to assume that an old speaker (30 years) will have lost a significant amount of its magnetization and need remagnetizing? Is this something that should be done routinely?