My Nepeta tuberosa tends to be damaged by the winds in early winter, so I cut it back to it's lowest leaves then.
My Nepeta Walkers Low is still looking lovely, but it will have to be cut back hard soon, as it has alliums and specie tulips under it and they will be up very soon.
It grows back steadily, just in time to cover the dying tulip and allium leaves later on.
Daisy