Does a tube need the break-in hours?

I wouldn't say they need to break in more that it's they need to be on through their infant mortality stage (first 50 hours or so). If there is anything off about the tube it will fail but after that the chances of living out its full two to ten thousand hours is greatly increased. That means  the tube is healthy and providing its best possible performance. 

I've had a tube preamp for over twenty years and could not tell the difference between a new tube and a "broken in" one after a 30 minute warmup. Same with my 2A3 amp, only that one sounds its best after the 2A3 has been hot for at least four hours, which I am loathe to do because I have the extremely rare RCA Cunningham single plate.

"30 minute warmup"

that's the ticket - do it

I have found and mfg state 100 hours to fully runin . The new metals need to season or settle in as in any metals they sound a bit bright the first 50 hours or so. Power tubes get hotter faster 
and tend to settle down quicker. Some specialty brands say 200 hours I think 100 hours is pretty safe bet.

12AT7 tubes can be called different things, but I am not aware of any substitutes.  For example, 6201 is US mil-spec AT and ECC81 is euro designation.  .

I have a bunch of US ATs and a fair number of Amperex/Philips/Valvo.

You might want to post a wanted ad with the specifics of what you are looking for.  The admins don't want us dealing direct.  I would be happy to post a listing if you let me know what you want.

Uncle Kevvy from Upscale told me the 12au7 and 12ax7 tubes which were NOS would take around 50 hours to break in.