Daisu,
I think you will get varying opinions about tube burn-in here. My view is that there are some very slight changes over the first several hundred hours, but these are slight. The tubes can smooth-out a little, but based upon your description, it seems unlikely the ones you have will ever be satisfactory. I would first try some speaker repositioning to see if that helps. If not, I would probably return or sell them rather than wait and see. Ah, the 'joy' of tube rolling. Good luck.
I think you will get varying opinions about tube burn-in here. My view is that there are some very slight changes over the first several hundred hours, but these are slight. The tubes can smooth-out a little, but based upon your description, it seems unlikely the ones you have will ever be satisfactory. I would first try some speaker repositioning to see if that helps. If not, I would probably return or sell them rather than wait and see. Ah, the 'joy' of tube rolling. Good luck.