What's the best way to make a program update from a new PPA (when an old one is no longer maintained)?

Let's say I'd like my FreeFileSync to update from 6.9 (the last version available in the official PPA) to 6.15 (the last version available on the official site).

There's a proper Vivid package available in GetDeb Apps PPA, but should I first disable ppa:freefilesync/ffs before I add this new repository to my system? Or maybe I should ppa-purge the old PPA? Won't I then lose all my FreeFileSync settings in the process? Maybe ppu-purge is too much and what I really should do is first uninstall FFS using a plain old apt-get remove (and maybe just in case backup FFS configuration files in the home directory before that), then disable the old PPA, add the new one and finally install the up-to-date package from it?

So many options. Which one's best? Please, help me get my head around it.

As far as my experience has gone since asking the question the simplest answer is: you just add a new PPA and let it update the package(s). The program settings stay untouched as per the usual update (because it is basically the usual update - the only thing that changes is the new source of the package(s)).