And as you may expect, capacitor reliability over time varies by manufacturer:http://www.electronicspecifier.com/Resistors-and-Capacitors/Low-ESR-high-rel-tantalum-capacitors-minimize-failure-rates-in-long-life-commercial-power-supplies.asp

http://www.avx.com/docs/catalogs/trj.pdf

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Interesting. If I ever use up the current stock of caps I have on hand, it sounds like I should look into picking up the AVX TRJ caps as replacements, if I decide to restock. I think I'm going on something like three years still with the original reels I purchased. The 47uF caps came on five qty. 500 reels, and I think I'm down to the second to last reel of those. So only 1000 of those left.

OUCH! I just checked the price on those AVX TRJ caps over on Digikey. There are two models of 47uF cap, both 25V (no 16V available), and the price, depending on the ESR, is $1.63 each or $3.18 each. And that's in quantities of 500 or more. Ouch.

I could actually kind of see spending that on machines I planned to keep forever. I think. But I doubt that very many folks would recap their boards at those prices.

There's an interesting article on Capacitor Reliability here:http://my.execpc.com/~endlr/reliability.html

When you open that web page, search for "Solid tantalum capacitors" to skip down to the right part. And if you scroll down even further, you can find a tantalum capacitor life expectancy formula.

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That is an interesting article. The main thing I took away from it was that one should use a 3x - 4x higher voltage rating on tantalum caps, than the expected voltage in the circuit. Unless the 47uF/16V caps are on the 12V circuit, I think Apple was already doing that with its aluminum electrolytics. 3 X 5V < 16V.

Still, while the tantalums won't leak onto our boards, it sounds like they don't last forever either. Sigh.