Any firm that says a power flush MUST be done on every boiler change and charge for it is taking money under fasle pretences and are using it to generate additional income out of the customers fear and naivety.
So, on that basis any firm that says that a Powerflush need not be done is scrupulously honest and doesn't make as much money?
Are you out of your mind? If you see a moody boiler install, and the customer is saying that their combi has been totally unreliable and needs replacing in 6 yrs, it is nearly always because of dirt; inadequate preparation.
I don't make more profit doing the Powerflushes; on the contrary, the job takes longer, is boring, and the cost is difficult to absorb.
It is the guys changing boilers in 6 hours that are making the big money. They are the ones misleading the customers. It is their boilers that will be going t*ts up in a few years.
I get very long warranties out of our suppliers; well in excess of 5 years in some cases. If my chosen manufacturers start getting sludge related call outs within the warranty period, I will lose access to further extended warranties and my customers will be inconvenienced.
Luckily, I don't get my business priniciples from those fitters on DIYnot who are simply too mean to buy the right equipment.
If you are going to take money off customers installing boilers, invest in the right gear rather than try to argue you don't need it.