I don't think that the "best practice" that you mention is really a "best practice." Did you read about this on someone's web page?
There seem to be a bunch of things that you need to
test for yourself.
There is no such thing as a single "production environment." There are hundreds of thousands of different "production environments" all around the world.
You should not base you software development practice on individual opinions and things you read on "web sites."
There is nothing wrong with putting an object reference is the session, if it works in your environment and meets your requirements effectively.