This is a very good question. If you poke around, you will find a lot of amp companies use Sovtek 12AX7WA or 12AX7WBs. Not because they sound great, but because they are bullet-proof. Just take a look at rjgtr's web site and you will see some reviews that really capture the sound of those tubes. I'm convinced you could heat them up, then beat them with a 2x4 and they wouldn't go microphonic. The only reason so many amp companies use them is because they are indestructible and won't break during shipping.
In my case, I usually ship amps with the tubes installed. I can't imagine any other form of packaging could be much better. Unfortunately, I just had an amp damaged by DHL. The tubes survived, but the cabinet did not fare so well...
http://home.comcast.net/~stvnscott/ship ... age001.jpg