Mixing preamp tube brands

I am still fairly new experience wise with tube amps,and have begun to dabble in tube rolling with some NOS tubes.My integrated takes 2 6sn7s and 2 6sl7s.My question is has anyone mixed brands for example 1 6sn7 tung sol with 1 rca, as a matter of course and what your experience has been. I know that I can simply try this and see for myself, but I'd like some views from folks who have done it. Thanks for any insights.