Hey Harley, it's definitely possible they were duds, it does happen, even when they've been well tested etc. If you like how they sounded in the Classic, I'd give them another go maybe from a different supplier ? Did they have any guarantee ? Not sure what Doug's return policy is. There's more than one story here about tubes being duds.
If for example a tube isn't pumped enough (maybe some issue when it was made ?) it will burn out faster as less good vacuum. This is one of the main reasons the old NOS tubes last so long as they pumped them for much longer back then. From an amp manufactures perspective, they probably don't want them to last more than a year or two so you'll have to buy new ones from them.
Like light bulbs, they can make them so they last for a very long time by pumping them more (as required for lights on ships due to vibration), same with tubes.