To mix or not to Mix!

Well today I was gathering the parts I needed to do my tranny fluid service, which I do every other oil change (I know overkill). I have been using Mobil Synthetic Dex/Merc for about the last 4 changes, I haven't had an issue and I WAS going to use it again, we were out of it. So to make a long story short, one tech at the shop said "grab the valvoline conventional" and the other guy... well...just say strongly disagreed about mixing the 2.... never crossed my mind till now, any opinions here?

I personally wouldn't blend conventional and synthetic anything. Yes, there are "synthetic blends" out there, but its not made just by pouring the two together........I agree with "other guy", wouldn't mix the two...

I agreed but, hthe other guy did have a point the bottle of Mobil says for top off or complete refill with any transmission fluid.