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.
Might not be a good idea to do that as then the tubes arent a matched pair.

I would think by doing this, that the sound would be different from each speaker.

Others will reply of what else could happen by using two different tubes instead of a matched pair.
If you mix 6SN7 tube brands in a component that uses only one 6SN7 per
channel, then one channel may (actually will) have a different tonal character
than the other.
I should have realized this point that both of you have made. I had seen reference on a tube supplier's site about a particular tube and how it 'performed better' if you will, when mixed in, but the amp may well have had a different configuration than mine. Thanks