I have not seen any Apple reference to a 30 day time limit for running apps. In fact if anything Apple says to download apps from your first country so you can continue to use them:
"Redownload your apps, music, movies, TV shows, and books on any devices that you might use to play or read them in the future. Some types of content might not be available in your new country or region. (Learn what types of content and services are available in your new country or region. - Availability of Apple Media Services - Apple Support )"
In my experience apps continue to run until they stop working because of age. The main thing that might happen is apps do tend to age after a while and require updating if the services offering the apps change things on their end. There is no fixed time and I have some apps that are 7 years old and still work.
The 2 ID method mentioned by Eric Root only really works if you are primarily interested in apps from the country to which the other Apple ID is set. You cannot connect to the stores in two countries at the same time.
In terms of what Eric was describing, you create a second Apple ID and then log into the App Store using that ID but keep you main ID for everything else.
Media & purchases - Apple Community
https://osxdaily.com/2021/10/29/use-different-apple-id-app-store-purchases/