Then just copy the files into another directory, or maybe include it in a VCS?

Extend the cleanup period to 2 years in ~/.claude/settings.json with

  "cleanupPeriodDays": 720

  PROJ="$HOME/.claude/projects/-$(echo "${PWD#/}" | tr '/' '-')"
  DST="$PWD/.claude/memory"

  [ -d "$PROJ" ] || { echo "No project dir: $PROJ" >&2; exit 1; }; mkdir -p "$DST"
  if [ -d "$PROJ/memory" ] && [ ! -L "$PROJ/memory" ]; then mv "$PROJ/memory"/* "$DST"/; rmdir "$PROJ/memory"; fi
  ln -sfn "$DST" "$PROJ/memory"

Yep, that’s what I’m doing, a cron to copy them off to the side daily