New Tubes- Need Burn-In?

Hey guys- a question.

I just put a new matched quad of Electro Harmonix KT-88EH in my Cayin A-88T Integrated. I properly biased the amp, and after a couple of hours of warm up there is still a touch of "glare" or hardness evident.

I know these brand new tubes need time to burn in...how long a wait is reasonable before I decide whether the EH tubes are the ticket or not? Any tips on what to expect?

Thanks!