Noticed recently that when I closed the bypass the fire would go down considerably, so I took a look at the catalyst, and a lot of the holes were plugged with ash. I was surprised since I had cleaned it at the end of the last season, have not run it much more than a month. Fortunately it's only a five minute job to remove the catalyst and clean it. The very small holes seem to catch ash and plug much faster than the large holed ceramic cat on my old VC Defiant Encore. Still loving how my stove performs, though. How often do other Progress Hybrid owners check/clean the ashes out of their catalysts?