Lowrider,
I have not heard anything about whether the Atmasphere preamp is hard on tubes on not. Other than a problem with the preamp, I am guessing you have had a run of bad luck. Is there a possibility the voltage from your power company is off? In a lot of places, voltage seems quite a bit higher than it should be and this makes some gear much more prone to failure. The maker of the tube amp and preamp that I bought is a custom builder living in Italy. Although I never specified voltage, he has made gear to match the specific voltage that the user is getting (he winds power transformers) from his utility; this makes a difference as to performance, and I would suspect, reliability.
It's been a while since I've last chased after 6sn7s. I never ran into highly microphonic versions of NOS 6sn7, although I bought quite a few weak tubes that supposedly tested "like new." Given the very limited stock of older tubes, the percentage of tubes that are bad must be rising as bad tubes are put back into circulation. But, I don't know of current manufacturers making anything like a Tungsol roundplate, which is why we keep foolishly searching.