I noticed all these high end super automatic machines have no descale sensor and rely on a timer. I found this strange as my $400 single serve brewer does have an actual descale sensor that detects when the pipes inside are getting clogged.

I was going to ask why super autos don't do this but I think I figured out why. I have a reverse osmosis filter that makes 100% pure water and this is all I ever used and I never got the descale message on my LCD in years of use (on forums people using tap water get the descale message very few months), except once when I put coffee ground much too fine for this machine, it has a very low pressure pump, the 2 Tbsp size filter is made of a thin plastic frame with a metal mesh filter:

http://ecx.images-amazon.com/images/I/41zoC4vkSkL.jpg

The pump was unable to force the water through them properly and the machine gives up before giving the amount selected on the LCD and the I get a descale request. Simply running a brew with the filter empty clears the descale request. So it's obviously relying on when the pressure exceeds a certain amount to request a descale.

This couldn't work on espresso machines because the pressure is quite extreme under normal conditions, so it can't rely on a rise in pressure to indicate descaling is needed.

Well I answered my own post before even submitting it but thought this could interest you.