It depends greatly on what you are doing. I've been coding in React for years now, but I _still_ use concepts I learned from Ember, Angular(1), and even non-web

It depends greatly on what you are doing. I've been coding in React for years now, but I _still_ use concepts I learned from Ember, Angular(1), and even non-web tech. Its all UI programming and in the end they all share much more than you'd think. These days I find I can take one glance at newer stuff (say, react hooks) and start getting ideas about how its used, benefits / limitations, even how its implemented, without spending more than 5 minutes looking at it. Relatedly, constantly jumping into new stuff can actually _hurt_ your progression because if you never master existing tech (find its limits, reading its source), you'll have more trouble seeing the relationships and trade-off's of the new stuff, and spend way too much time just learning API's without gaining any intuition.