Easting. I agree that there is no need to flush if you regularly change the coolant, and I also am a big believer in the benefits of freshwater flushing of the salt water cooling system. I do it as often as I can (takes less than 10 minutes) and leave the boat with a freshwater with Salt Away mix in it all winter.
However, even with that preventative regime, I still recommend regular (although regular freshwater flushing coupled with the proper aftercooler reassembly including pressure testing will reduce the required full maintenance frequency) aftercooler maintenance at least every 3-4 years. Freshwater flushing will not clean the air side of the aftercooler and dissimilar metal corrosion can still become an issue.
I agree totally with you, but I was also wondering whether Helm was also flushing the coolant side annually as well as replacing coolant. Just curious