It seems every time I use the Excalibur II 1000 I encounter a new problem.
I understand that the analog portion of its design allows the user the ability to rapidly change modes, threshold, volume, sensitivity, and discrimination without the need of a visual display. And that the wider variance between analog components verses digital components is the reason why there is such a difference between Excalibur II detectors (some being hot, others being not).
The analog components are also this detectors Achilles heal as the knobs to the pots are easily broken or stripped, pots tend to develop rough spots over time and switches freeze or become intermittent.
In addition there is always the danger of fraying / breaking/fatiguing the cable to the hard wired headsets (which always seem to fall off) and the search coil. Especially if you are use hip mount, chest mount or back mount for the control and signal processing tube and the battery pod.
Though the digital components are highly reliable, little is known about the controller, and less is known about the algorithms that are used to process the selected 17 frequencies.
This detector appears to be like a guitar in that it is easy to use, but difficult to master.
The question(s) that I am trying to get around to ask and need answers to is:

1. With such a wide variance in performance between individual detectors and such limited information on how it's software works how do you know if your detector is working properly?
- Or put otherwise are there any benchmarks that your Excalibur can be compared against?
2 For other than catastrophic failures, when should the detector be returned for repair? It seems like I encounter a different problem every time I use it.
As I live in a remote location and hunt alone, I cannot compare one detector against another, and there is no metal dealer nearby.
3. I have heard that it is better to tune your detector to the beach you are detecting rather than use auto sensitivity, but do not know how to determine when the detector is properly tuned.
4. My detector is more stable in the discrimination mode than in the pin point mode.
It also detects coins deeper in the discrimination mode than the pin point mode.
I find this puzzling as it is supposed to be the other way around .
I use the below switch and pot settings at the beach when hunting on dry sand, wet sand, and in shallow water:
Power - On
Mode - Discriminate
Sensitivity - Auto, as I am trying to learn the detector.
Threshold - faint buzzing mosquito, to below where I can hear it when there is a lot of ferrous metal
Volume - Maximum to be able to hear faint deep targets. Use wet sponges in ear cup(s) to dampen loud returns from shallow coins.
Discrimination at 1 , increase to 3 if there are a lot of bottle caps to make it easier to distinguish them.
Oh by the way, though I have not yet had to send a detector back to Minelab for repair, my experience with Minelab in answer(s) to my question(s) and in providing parts that I could repair myself has been favorable.
It is probable that they are replacing more than the part that failed as such failures can cause stress increasing the probability of multiple failures later. Also, by replacing parts with high failure rate(s), customers will be more satisfied as it is less likely that they will have to resend the detector back in for repair. As a customer, I am very grateful when any company does more than it is necessary to repair the item I sent in, especially if it only cost me a few bucks more since shipping costs to and from where I live are high.