[bm98]

Software lifetime is an interesting topic. See for example [1], a 1992 paper that surveyed business applications and found an average lifetime of about 9 years, with a maximum of 20 years and a minimum of 2 years. 2 years versus 20 years!

Things don't seem much different today.

On the one hand, HTTP, HTML, and producing HTML server-side in a language like Java or Python and with a SQL database isn't all that different now than it was 20 years ago. There are Java web apps developed in 1999 that are kept up-to-date and work just fine in 2020. On the other hand, there are applications developed with popular technologies a just a few years ago that are hopelessly out-of-date and in need of a rewrite today.

I see it as an end user too. I've been an ING Direct (now Capital One 360) customer for 18 years. The web app that I use in 2020 seems to do the same things as the one in 2002 (though it's slower today), but it seems like it's been completely rewritten at least three times.

[1] https://scholar.google.com/scholar?cluster=23826996884004375...

EDIT: And HN! 13 years old and counting...

[adrianN]

I'd bet that some of the systems that were 20 years old in 1992 are still running.