As I think about all the technologies that have come and gone, it's good to find some sturdy rocks as well. Here are some techs that withstood the test of time in my personal journey:

* Simple, but reliable file formats: My old photos collection is 25 years old (jpeg) and I still look at them occasionally.

* My influxdb/grafana/openhab setup is now 8 years old and has been operational with only minimal hickups.

* Some home automation scripts I wrote have endured for 8 years now.

* My Linux/Unix knowledge is 26 years old (although much has changed since Slackware).

* My C and C++ programming language knowledge is 28 years old (although I rarely use it anymore, because of Rust). Occasionally it is useful during debugging performance problems in kernels.

* My knowledge of distributed systems (stuff like leader election, distributed and centralised algorithms) is 15 years old. It is still very relevant to understand both existing systems and to evaluate new systems.

It is crucial to distinguish the knowledge that stands the test of time from the fleeting trends. And finally then there are the non-technical skills, which pay off even more. Effective communication, negotiation skills, organisational finesse, inspirational leadership, adept management... These are the true constants that support us during our professional life.