If you leave the EU for "too long," you won't be able to update apps installed from alternative app marketplaces.
This is not the case for the App Store. A German account can install apps and purchase content from the German App Store even if you're gone for "too long"
@mysk How do they know I left the EU? IP or location services? Maybe there is an option to use VPN or turn off one location service in privacy settings

@anonimowy

"The country or region of your Apple ID must be set to one of the countries or regions of the European Union, and you must physically be located in the European Union."

https://support.apple.com/en-us/118110

About alternative app distribution - Apple Support

Users in regions where alternative app distribution is available have the ability to install apps using alternative app marketplaces or web distribution, in addition to the App Store.

Apple Support