Jon: I have a fully setup v1.3 with x add-ons.

At the end of this month, before the next payment for the dev license I want to change to Academic. When I buy the license will it automatically replace the dev licence without any special action on my part?

From what i know,

The dev version and the acadmic versions are not the same and the codes you get for the academic version wont work on the installed dev version, you will have to download the academic version of P3D and install that.

Make sure you backup the locations where custom content has been installed first ( like effects. simobjects, gauges etc ) and also backup exe.xml, dll.xml and the controls folder for quicker restoring of your files and settings

I know its a pain to do but once you have a good backup you can use it again if something goes wrong.

Paul