Storing tubes in a freezer is not a good idea. Yes, the freezer is a low humidity zone, but what happens when the power goes out and that unused Thanksgiving supermarket freebie turkey decides to melt down onto your KT-88's while you're on vacation? Keep in their original boxes in a solid, crush-proof environment (I use an old trunk) and if your worried about moisture, add silica gel packets or even a chemical dehumidifier tub, available at hardware stores. And I have a quad of Electro-Harmonix EL-34's that were cryo'd that I paid $15 extra for the treatment. I have compared them to identical tubes that were not cryo'd, and there is a difference. The treated tubes have a more focused sound and their midrange and treble response is more liquid and warm. The cryo'd tubes sound more like SED El-34's, and less like EH. I'm very pleased with them and I have many types of power tubes at my disposal. Also, their burn in time was approx 40 hours until I stopped noticing changes in tone. 750 hours is probably at least half the viable life of a modern power tube.