Do you have some sort of guidelines when and when not to do hot release upgrade?

I still have to find anybody shipping whole updatable releases with erlang - couchdb, rabbitmq, any big open source project, nobody is doing it. I think it's a bit overrated, because realistically nobody will want to do this in production, unless it is audited and tested in every possible way. If you have to update external resources with the code_change callback it can fail miserably. I have no problem using it in production for small changes that I fully understand, but big release - wouldn't do it. Too many things can go wrong at the same time to react. You have to audit and test the upgrade and the rollback, which means extra code in code_change to handle the rollback too. Quite heavy.