[smart-assed remark] Hey I've got an idea. You seem bent on spending extra money. Just grab the tubes you want, and send the extra to me.
[/smart-assed remark]
The Gear Page (aka rich people who can afford real $75K Dumbles) on Cryo tubes
Bottom line: waste of money. You can buy NOS tubes for those prices.
MAYBE you can tell in high end tube audio gear, but in a guitar amp that you're going to be running with distortion? I don't think so. And as is stated, the cryo treatment may weaken the structure inside the tube.
You don't know if the tubes will actually last longer because the tube may have lasted the same length of time without the cryo treatment. Maybe even longer. Maybe that was just a good batch of tubes.
NOS preamp tubes (the real deal from places like
http://www.kcanostubes.com ) should last about 10 yrs for preamp tubes and about 2 to 3 yrs for power tubes, but I wouldn't spend my money on the power tubes because you could end up with a bad set anyway. It's a crap shoot with electronics.