There is a persistent myth that an app is a project with an end: you build it, you launch it, you are done. In reality, launch is the beginning. An app is a living thing that starts decaying the moment you stop tending it, because the world it runs in never stops changing underneath it.
Apple and Google release new operating system versions every year, sometimes breaking things or requiring changes to stay compliant with store rules. New devices arrive with new screen sizes. Libraries the app depends on get updated or deprecated. An app left untouched will, over a year or two, start breaking, look dated, or get removed from the stores for falling out of compliance. Standing still is moving backward.
Security is the other relentless force. New vulnerabilities are discovered constantly, in the app's own code and in its dependencies, and an unmaintained app accumulates unpatched weaknesses that attackers can exploit. For any app handling user data or payments, ongoing security maintenance is not optional; it is a duty that does not end at launch.
Real maintenance means keeping the app compatible with new platforms and devices, patching security issues promptly, fixing bugs, and improving based on how people actually use it. This is why we handle updates for the life of the product rather than handing over a build and walking away. An app you own is a relationship, not a purchase, and treating it that way is what keeps it working.
You do not finish an app. You keep it alive.
This is general educational information about building software, not specific technical or business advice.