Environmental Variables, are they live? and how do they work with P&D?

so I ocasionally make use of environmental variables, because if I want to be able to test in Dev, I don't want emails going to production distribution lists, I just want them going to myself.
The problem is that even though in Dev I have a different value for Dev Environment Library and another value for Prod Environment Library, when I package and deploy, it always transfer the Dev value from Dev Instance to the Prod value in Prod Instance (which means the Prod value in the Dev instance has no effect), also are they live? because even when I go and change the value in my Prod instance, it still uses the original values. So does the workflow save the values from when it was made? or is it supposed to use the value that the variable has at the moment? I'm very confused.