Catalytic combusters are delicate: the paladium or other precious metal coating on the ceramic grids is fragile. Blow out or brush carefully.
Sud-Chemie and Corning, makers of cats, have a manual ( maybe online ) that shows how a good combustor should look, and pics of deteriorated cats from too hot flames or trash burning, or higher than normal heating.
One renewal method that has worked for me is to literally bathe the cat in a flat pan or plate of warm vinegar--be sure that SWMBO is out of the house if done on the kitchen cook stove.
The instructions for this usually come with a new cat or on the maker's site for details.
I clean and check the cat at least twice each heating season. Since we use the cat stove 24/7 in winter, the cat's life is around two years, maybe three if the winter was mild.
For efficient, long, consistent heat, our cat stove does a better job than the non-cat for a similar space and insulation. Replacing the cat every 2-3 years is just part of routine maintenance. Forget the "12,000 hour, or 6 year 'prorated' life" of a catalytic combustor. Used hard for 100% wood heat in a normal northern winter, cats last less than the 5 or 6 years they warranty.