In 20 years, it's gone, the business requirements are unpredictably different, probably the language I wrote it in is gone too, maybe the entire company as well

In 20 years, it's gone, the business requirements are unpredictably different, probably the language I wrote it in is gone too, maybe the entire company as well. I'm writing application code, not a kernel or something, but even kernel pieces have API boundaries and can be replaced. An API can live 20 years, so I take that far more seriously.