I have been considering disc brakes on a tourer. For what it is worth, it seems to me that a couple of points emerge in this thread, leaving aside those that dogmatically prefer one or the other.
One point is the quality of components; It seems that neither the qualities of pads, discs, brake blocks or rims are revealed quantitatively by manufacturers or known by users.
The other is that in fact the real weight issue probably comes from needing different fork and stay characteristics rather than the brakes themselves (although them as well).
It appears that many cycle parts manufacturers seem to spend large amounts of money on starting fashions and advertising, but very little on the actual components they wish us to buy. Never mind finding out what actually improves or extends the cycling experience.
Bearing in mind that especially perhaps in this context, motorcycles, have brakes which last far longer, stopping from far faster a much heavier machine, with brakes that relative to the machine and speed probably weigh far less, over a similar range of conditions.
It would seem to me if anyone is interested enough that it might be worth approaching a large brake friction material manufacturer such as; Ferrodo, or Mintex (Anyone here a technician in this industry?) to find out quantified information and any particular difficulties that may be peculiar to bicycles, in order to obtain the best materials.
In my view except possibly in the most extreme of off road conditions, if your brakes don't perform for several thousands of miles, they are not fit for purpose. You can't really over heat rim brake blocks because the tyres will pop first (the only reason I was considering discs).
Wheel rims do not 'suddenly' wear out over one weekend - this is maintenance and servicing in the hands of the user.
If one has hydraulic oil leak problems, cheap vegetable cooking oil can be used without further damaging seals in an emergency. Brake fluid is vegetable oil with (highly toxic) additives to dissolve air and emulsify water (to stop it boiling).
Anywhere their is a motor vehicle there is brake fluid; even in India.
Bearing all this in mind and using the edict of simplest and universally repairable and understandable is best for touring; for the time being discs are out for me. I hope everyone else keeps using them because then they will get better!