300b tubes burn in time?

I just bought a new pair of Shuguang Black Treasure tubes. For some reason they don't sound as good (open, detailed, life-like) as my old ones of the same brand. 
Do you know how many hours 300b tubes take to fully burn in?

Or I am wondering if I got some sub-par pair of tubes.
I'm sure you've already asked yourself this question but do you recall if your old ones sounded great right out of the box or if they too blossomed with decent burn in time?

Same brand and model or did you have another model from Shuguaug. I know the Black Treasures and WE's sound quite a bit different. That's said they do take a 50-200 hours to settle, so give them at least 50 hours.

I personally found the treasures to be less detailed then the WE's and the WE less over all then the Genelex gold lions.

Maybe it wasn't your output tubes that needed replaced?  Have you checked the gain or other tubes?  A worn out 12 series will make the 300b sound flat.  These shouldn't need burn in at all.
Also, have you checked your bias?
I bought the amps used, so the old ones sounded great all throughout (they must have had a few hundred hours on them at least I figure).

Same brand and model of tubes. Black treasures.

The other tubes should be fine (I think), since the old tubes gave great sound (I didn't replace them, its just one that I mishandled the amp and one of them broke) so am replacing not because the old tubes seem worn out, so I know there is still good sound if I still had the old tubes.

My amps are supposed to be auto-biased.

It's just not sounding that open or lively compared to what I am used to with this amp.