If I were to make a lot of assumptions, you are probably going to need something that can compile statically into a (mostly) self-sustainable binary. That means

If I were to make a lot of assumptions, you are probably going to need something that can compile statically into a (mostly) self-sustainable binary. That means Java and C# .NET are out. You can use a GUI, but only if you pin yourself do a single OS and single GUI system. For a macOS/iOS target, I would say: Swift. It mostly compiles down to a single application (well a bundle...) and the native frameworks supply persistence and UX methods that last long enough to be considered 'a long time' by my personal vague concepts. For Windows, you'll be stuck with something like Win32 C++. For Linux, you'll probably be stuck with a choice between GTK and Qt, and again something like C++. If you don't need to target any of those systems specifically, or you don't need to make use of a UI, you can do Rust or Go for all/any of them. If you want to do something for the web, you are screwed. You'll always end up targeting a scoped set of browser versions, use something that either is or compiles down to CSS, JavaScript and HTML (3 languages at least), and if you run a server component, that requires maintenance too (even static file serving). Nothing on the web really 'lasts a long time' as-is.