Every time I think about implementing this I realize the categories I have today and the categories I have five years from now are unlikely to mesh well.
At least based on my priorities from five years ago.
I've been thinking about that too. We either make broader categories or allow ourselves to deprecate and refactor category numbers in the future.
To me though the overwhelming benefit of the process is the act of bucketing. Another strategy then would be to bucket down to 8 categories instead of 10 — like line numbering in BASIC you allow yourself a bit of space if needed in the future.
At least based on my priorities from five years ago.