Question about heat exchangers of a fresh water system

Good day. I would be interested in the following. We have a pellet system including a fresh water system in our new building (just under 4 years old). I was present during the maintenance (so to speak, I observed). And I noticed that the heating technician did not service the heat exchanger of the fresh water system at all. I have already read quite a bit online that the heat exchanger, with normal water hardness (we have 11 degrees), calcifies over time and thus delivers less performance. I asked the heating technician why he does nothing about it. He says he would only replace the heat exchanger if the temperature differences become too large. He has measured that. It is still okay. When asked why he does not descale it (the manufacturer says to simply connect a descaling pump to the heat exchanger), he says he just does it that way... Isn't it uneconomical to completely replace the heat exchanger every few years? Descaling would be more economical in the long run, wouldn't it? Thank you