I have to say this without any hesitation...my replacement 10"D2 I got last week has been a blessing in performance, finds silvers, and is fun. The sig losses now are not even 2 digits until I get to nearly RX15. The D2 passed RX15 open air(no OL) up until the week before, but the signal losses were terrible all the time.
It just bugs me that the factory labeled term "signal loss" was made, and some people report less that 20% all the way across the gain window, and yet other give numbers like 50-60%. If the term signal loss stands for anything at all, then why is there so much variance between users. Remember now, lots of these reports are in open air applications, not a dependency of local soils.
Signal loss degrading or not will be something I will personally monitor. If it is stellar when brand new and then hits above 20% fast...I am making a record of it. I have never, and I mean never enjoyed a D2 coil in 3 whole years, but I admit that I didn't ever check the signal losses with the other coils.
I would really like to know where the loss(power) goes. It is a real number or else it wouldn't be trackable, right? Is it all software? Is it a performance inhibitor? What? Something changes or else it would remain as it was on day1.