I have a Rust web project written ~5 years ago. Zero updates until a month ago, also zero problems. A month ago I upgrade the docker file to latest rust, zero problems compiling. Could have left it to run like this for 5 more years probably but I decided to experiment...

I issue a `cargo update` to upgrade the leaf dependencies and do automatic minor version updates. Issue cargo check. Some new warnings from `clippy`, but it still compiles and runs without problems. Could have deployed for 5 more years, but I decided to experiment more...

I upgrade some of the libraries to major new versions - I am experienced and I know which ones will upgrade without problem. They do upgrade without problem. Could have deployed for 5 more years but decided to walk the extra mile...

I upgrade the more problematic ones, especially actix_web, the web framework, which had a massive rewrite and a huge new release with almost completely different API surface... It's a bit difficult to understand the changes, especially some parts of the old code written for the old version (which I no longer remember), but in an hour I'm done. Afterwards `cargo outdated` does not report any outdated libraries. I deploy for the next 5 years. Zero problems since then.

Well, it's not decades yet, but I can imagine similar effort to maintain it over the next decade.