What is proper way to upgrade to nightly builds and new stable versions?

[MetalMania]

Hello

Lets assume that we have fresh installation of avidemux.
Now we download nightly build and overwrite all files in program installation
directory. When next nightly build is available is safe to overwrite all files
again? (nightly build over nightly build) or all should be restored to latest
stable version and than overwrite it again with latest nightly build?
Sam question goes for new stable version. Is its safe to just overwrite old
version or it should be removed prior to installation of new one?

[mean]

you can overwrite or put it in a separate directory