This would heavily depend on your particular usecase, but the general idea is to have a command that would move your photo/video files from the mobile-synced directory to the “permanent” directory, and then have that command run on schedule.
The command can be as simple as mv photos_from_mobile/* photos/, or more complicated (I wrote a script to have it organized by year and month, for example). One thing to keep in mind here is that you don’t want to move the files that are not (yet) fully synchronized, so whatever your command ends up being, make sure it doesn’t move .syncthing.* files.
As for running the command on schedule, there are multiple ways of doing that, depending on the operating system you’re using and your personal preferences. For Linux, the traditional way is setting up a Cron job, but newer and more versatile options are available. How often to have the command run is, of course, up to you.
Don’t be shy about your English, it’s not my native language, either. 