(Should have mentioned this in the last post. Oops!)
You've littered your tree with debugging commits. Or you've landed a patch without pushing yourself, so it exists upstream already and you don't need your local copy. Slowly but surely
hg wip becomes less useful.
Works just like your garden's pruning shears. Except, it's powered by Evolve, and so really it just marks changesets as obsolete, hiding them from view.