Unfortunately, knowledge decays over time. https://en.wikipedia.org/wiki/Forgetting_curve
Personally I find that knowledge that’s internalized and used does not decay. And devoting effort to refreshing the DRAM for knowledge I’m not using seems like it fails the YAGNI test. Let my brain’s cache eviction algorithm do its thing. If I learned something once I figure I can probably learn it again.
Surely using it is a repetition of it, essentially?
I always figured spaced repetition was a tool or help with knowledge you didn't have opportunity to apply otherwise