My boiler has bees going for about 5 weeks, and after seeing your post I decided to take a look. I had quite a buildup of fly ash as well, not as bad as yours but close. So now I plan on getting out the vacuum every 4 weeks.
You are going to shut the boiler down every 4 weeks? It took me all evening to shut it down clean it up and restart. I can't see doing that all winter long.
As stated in the manual, it is not necessary to shut the boiler down for cleaning, and in some cases it may be needed every month, but shouldn't take more than two to five minutes (you have the clean out option which makes it lightning quick). Clean each tube by placing the vacuum hose over the outlet and sucking out the fly ash (simply turn off the switch while doing this if you have any concern for CO). My number is in the manual, please call me if you need any more information. Also make sure you use your draft gauge to monitor the base draft so that you can clean it when it starts heading south of -.01" WC. That way you won't have to shut it down due to a CO detector going off.
Thank you for taking time to post your experience on the forum, it is good discussion.