I've been writing code for 40 years (first computer TI-99/4A). Honestly, it's all a blur and anything older than 4-5 years is irrelevant history.

There are many concepts useful that are decades old e.g., you could learn shell pipelines in 7x and use them to this day. Once learned, you can reuse indefinitely the notions "tight cohesion", "loose coupling" (just an example), etc.