DNN development and production sites

Bro John wants me to write up how he does DotNetNuke (DNN) upgrades and site copies. As a preamble, he wrote this:
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I would think anyone with a production site would want three copies
A - a live site
B - a transition site
C - a development site

also
D - a trash site

As most of my stuff is now in phdcc.CodeModules, I develop these until they work on C, I copy these to D to see if they still work in a different environ. I then copy them to A and test.

I would prefer to have a B which means I can shut down A and have users running on B and then swap back to A later if for example I do a DNN version upgrade.

Doing a DNN version upgrade on a live site is just asking for trouble.

If this sort of stuff is not sorted in DNN properly then I wouldn't consider it a solid environment to do anything serious in.

I am trying to be careful about keeping all database/email server specific stuff in a few files. Hard links to other pages on the site are OK if you copy the entire site correctly.

Maybe bigger players have other tricks they pull. Maybe they swap DNS pointers. However that takes time to permeate and produces horrid cahcing problems.