I have "back mixed" powders pretty regularly but there are some precautions.
I have some Win 231 left over from before Hodgdon took over the distributorship and started packing W231 and HP38 out of the same barrels.
That old (metal can) 231 is markedly different from my present supply of HP38. So I will not be combining those, even though Hodgdon shows them to be the same now.
Accurate Arms has sourced powder from all over the world. I would look to be sure two cans of A2230 were from the same country and that the appearance was the same before combining them. The five year business is no guarantee if they changed powder mills at the 3 year mark. Even with the same number designation and alleged same burn rate, I would not combine powder from different factories.