For the rest:
This is an excerpt from the Q & A page at the Weber VST website. The answers are from Ted Weber himself. The man knows speakers!
I recommend spending some time browsing this site. There's a lot of good information here. In particular, I found the user comments very helpful when I was deciding what to install in the Ampeg VT-40 I rebuilt last year.
From: Shawn Bolton
"I think I understand your explanation of the differences between AlNiCo and Ceramic magnets in speakers, but what do people mean when they say modern AlNiCo is different than old AlNiCo or that it has a half-life?"
"Shawn, I hadn't heard about the belief that old and new AlNiCo are different, however they are one and the same. For speaker applications, AlNiCo 5 is the best choice in the AlNiCo family of alloy magnets. Its peak energy product is just right for loudspeakers where we need to concentrate high densities of magnetic flux in the gap around the voice coil. AlNiCo 5 is an alloy made up of 8% Aluminum, 14% Nickel, 24% Cobalt, and 3% Copper. The cobalt is what makes the AlNiCo expensive. Most of the worlds supply comes from the African country of Zaire. Besides that country controlling the market, cobalt is also a strategic metal used in missles and other weapons systems. It currently sells for about US $32 a pound.
As far as it having a half-life, that's another new one on me. When a speaker is put together, the magnet is initially uncharged, or unmagnetized. Then, at the end of the assembly line, just before testing, the speaker is passed under a huge electromagnet that zaps the magnet with about 10 to 20 times the magnetism that would be required to saturate the magnet. After the electromagnet is turned off, the speaker magnet immediately loses about 2% of its magnetism and then stabilizes. In the next year, it drops another 1%, and then is essentially stable for thousands of years. Unlike a flashlight battery, the magnet is not being used up or depleted of its energy while in use. All that has happened is that we have forced many of the tiny molecular magnets called domains to realign themselves in one direction. Once 'flipped', they reach an equilibrium and stay there. Besides intentional demagnetization with a demagnetizer, there are three situations that can cause a magnet to become partially or fully demagnetized, and this may be what the half-life comment is all about. The first one is excessive heat. That's not a consideration for speakers because the temperature to demagnetize an AlNiCo magnet (called the curie point) is over 1000 degrees F. The second is from a large, changing magnetic force. This could happen in a speaker. The typical case would be where a person blows out the speaker by using excessive power. The high value of magnetism produced by the voice coil could partially demagnetize the magnet. This is why you should always ensure that anyone who is going to recone a speaker for you have a magnetizer to renew the charge on the magnet, just in case it got partially demagnetized. The third and final situation is physical shock. If you dropped an AlNiCo magnet speaker and it happened to land on the corner of the magnet frame, it could partially demagnetize the magnet."
:)