Applying SSIS Package Configuration to multiple packages
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I have about 85 SSIS packages that are using the same connection manager.
I understand that each package has its own connection manager.
I am trying to decide what would be the best configurations approach to simply set the connectionstring of the connection manager based on the server the packages are residing on. 
I have visited all kinds of suggestions online, but cannot find anywhere the practice where I can simply copy the configuration from one package to the rest of the packages.
There are obviously many approaches such as XML file, SQL Server, Environment Variable, etc.

All the articles out there are pointing to use an Indirect method by using XML or SQL approach. Why would using an environment variable for just holding a connection string is such a bad approach?

Any suggestions are highly appreciated.

Thanks!