Do codes stack?

[Gizm0]

Do the 3 months of pro stack, I bought the FE and am thinking of buying PE so I can have a second controller and CCU on another TV.

[Ivan]

@Gizm0 I don't think that's the case. The 3 month Pro seems to be considered as a 'trial' system. So if you get Premiere Edition, you will need to create a new account to use the 3 months Pro.

But if you want official response, you can try confirming with Stadia support.

[mcnichoj]

I might buy a PE for the second cast/controller so I can play it at two different places and not have to worry about lugging things back and forth.
My suggestion is to just try and sell the PE code. Technically the code is worth at least $30 but due to the exclusive nature of it only being in bundles, you could probably ask for a little more.