another rider who has ridden and toured on, and does ride, cantis, v brakes and mechanical discs
yes, discs work great and I appreciate how less hand finger pressure = same or stronger braking compared to my cantis , BUT cantis work fine too and like I always bring up, its like downhill skiing--you simply have to have the judgement of what stopping power you have for a given snow and ice surface and know when to rein things in for a given situation to be able to slow down enough for unforeseen things like another skier pulling out in front of you from a narrow side run, or an unseen steep icey pitch that appears....bottom line is that yoiu have to have proper judgement.
same with driving our cars, or riding a motorcycle or whatever.
next topic up--proper braking: the front brake slows us down a lot more than a rear brake, so use the front hard is key, you aint gonna flip your touring bike over--ever.
and do not drag your brakes, use hard applications of both brakes, more force on front wheel, and you will slow down faster AND then release brakes, dont drag. Dragging just heats up everything and you degrade your braking power.
This happens in a car or a motorcycle or a bicycle on long downhills, so no dragging.
Check speed and slow down with a good hard application of both brakes, more on front--let bike run a bit, reapply another hard application of brakes etc. Obviously dont let the bike get going too fast to control--go back to skiing example....cuz then you get into potential trouble.
so sure, I find that with discs I have more wiggle room because of the increased braking power, but hey, lets be realistic, its pretty rare that we are on downhills that we get going fast, so just use judgement and keep speed in control, and all of us have done this with whatever brakes we had on our touring bikes in the past.
and yes, you can overheat discs also, just like you can overcook disc brakes in a car if you drag too long on a long descent....so brake properly and keep things in check, its that simple, even with cantis.