dvcavall :
through repeated sharpenings, or touching up the edge for one reason or another, the edge would need to be reground to maintain the same edge profile.
Yes, if you only hone on the flat part of the bevel, eventually you will remove the convex part completely and basically convert the edge to a chisel profile.
I am guessing, and it's only a guess, that the reason you recommend ceramic and not diamond sticks, is because they remove less metal.
There are a number of reasons why I would not use a diamond rod on the knives. First off the blades tend to get used for a lot of high impact work, and for that you want a strong edge which means a high polish. A diamond rod leaves a very aggressive slicing edge, but one that will quickly break down during any kind of chopping or prying/twisting as the micro-teeth break off and leave large blunt patches.
As well, like you mention Diamond hones are much more aggressive at removing metal. When using a knife for heavy work you tend to cause blunting by edge deformation/impaction. Using a diamond hone would tend to strip away metal when you would want to align it, which is wasteful. While excellent for putting a quick edge on a $10 kitchen knife, this is not something that you want to be doing on a regular basis to a high end blade.
However personal preference does play a part in sharpening, there are a number of people who like the higher slicing aggression of rougher finishes. The best method for you is to simply experiment and find out which method gives the edge the best combination of cutting performance, durability and edge life.
Also, is it obvious to the user when the asymmetrical edge needs to be reworked
The change will happen very gradually, it is like growing taller, the increments are probably too small to be significant on a daily basis. What you would notice happening as this progressed is an increase in cutting ability, a decrease in edge durability and a greater skew happening during the cut. It is critical to note that it would take a huge amount of sharpening for this to happen combined with a total lack of honing of the convex part of the bevel. Even if you simply worked the edge with a loaded strop on occasion (which you should for maxium edge life), it would significantly increase the time it took to remove the convex part of the edge profile.
Being more specific, unless you were doing something like digging in the dirt on a regular basis, I would be very surprised if you had to sharpen the knife to the extent that it needed to be returned for a reprofile even every couple of years. It takes an extreme amount of work to wear any metal off the edge unless you beat it off. For example, when I first got the blade I attempted to wear the edge down on chopping wood to the extent that the edge was dull enough that it reduced the chopping performance significantly (10+%). After cutting about 10 000 pieces of 2x4's worth of wood (I wasn't cutting 2x4's that is just the rough equivalent, and the reference is clear pine, 7 chops to be specific), I still had not moved beyond needing a loaded strop.
Currently I freshen the edge on sandpaper every once in a while to recut the carbides so the blade will slice aggressively and maintain a high level of edge strength and overall durability. Note that this honing on sandpaper doesn't remove a significant amount of metal, its significantly less than 1/10 of a mm (I measured the edge width with a micrometer before and after sharpening a few times). I go to the sandpaper after some honing on a loaded strop doesn't produce an edge which shaves smoothly and/or doesn't slice as aggressively as I would want.
In terms of overall metal removal, I have probably taken a mm or so of edge off of my Battle Mistress through extended honing sessions. These were never required for sharpening purposes, but were done to either reshape the edge (make it more acute), or to remove damage caused after test cuttings on hardened metal (nails and the like). Note I tend to let such damage accumulate, I don't grind out every flaw in the edge, if I did that I would wear the blade down far to fast. See the next paragraph for more details.
Being a flat ground knife (BM), and a heavy knife, the profile probably gets fairly thick,fairly quickly.
I had a Basic #7 that went through hell on earth for 2+ years and was used for the most aggressive "cutting" I have ever seen. It was sharpened excessively on a belt sander (don't lend equipment to hillbillies, especially when they are family) and vastly reduced in size. It still cut very well. The chopping ability had been reduced significantly due to the loss in mass however :
http://albums.photopoint.com/j/View?u=1514533&a=13372300&p=50884869
Guess which one was mine.
-Cliff