The useful second brain is not a life log.
For me, the shape is closer to three layers: raw inputs, maintained wiki pages, and generated outputs. Raw notes stay messy. The wiki layer gets maintained. Outputs are briefings, summaries, drafts, or decisions that can be thrown away or promoted back into the wiki.
The mistake is asking AI to search the raw pile forever. That turns every question into archaeology. The better pattern is persistent synthesis: keep a maintained layer so knowledge can compound.
The raw material still matters. I just do not want to reread it every time I ask a question.