Have you set up a password-protected version of your forum for testing purposes, or do you fly by the seat of your pants?
AA has a test forum, yeah. I also have a personal test forum that's more of an experimental place to try new ideas for anything as apposed to a specific forum (but it did start as a test forum for a specific forum). I do a lot of work and messing around there with the luxury and privacy of password protection and the fact that this forum will obviously never "open" so it doesn't really make a difference what I do.
It is very handy and virtually harmless (it actually prevents harm from being do to your real forum).
2 copies for my 2 vB licenses. Very handy to have when trying to upgrade templates and test plugins, especially when I populate it with a later copy of the database.
I have a test site for Bird is the Word, but not for Setsou - I guess if we ever decided to test something, we could easily set up a sub domain, install MyBB and get testin'.
Yes, my test forum comes in great handy. It's like a bomb went off in there because I really don't think before I do anything - I just try it. Yes, no harm will be do to your real forum.