How involved is de-CARPing an installation? We currently have two boxes running in a CARPed (mirrored) set-up. As the 2 PCs they are on are getting on a bit, we had planned to stop using them in a CARPed set-up and have pfSense running on a pen-drive which we just put into one computer. And then swap the machine used every two or three months. And regularly re-clone the pen-drive!
Long term, the plan is to upgrade from 2.0.1 to the latest version - with a backup of the settings available to revert if we need to!! Trouble is, I can't find a download of 2.0.1 at the moment.
Make the upgrade from the GUI and check "Perform full backup prior to upgrade" first. So you have your backup just in place.
Alternatively pull an image from the disk first with clonezilla or somewhat like that.
Read the upgrade guide first:
To switch from CARP back to a stand-alone unit you can remove the sync settings from System > High Avail Sync and from the DHCP server tabs. CARP VIPs and NAT can be left as-is.