Make sure you cranks are fitted properly in the first place. Do you have a square taper BB or splined one ? I haven't tried self extracting bolts on a square taper, I doubt I could get enough torque with an allen key, rather than a socket driver, to pull a crank with self extracting bolts. If you have a square taper, allen key bolts will allow you to tighten the cranks if they come loose. They shouldn't come loose though, something is wrong if they do or they haven't been tightened enough, which is also wrong.
I never carry cone spanners either, nor any means of removing a cassette (though to be fair in my half way round world ride I had a uniglide cassette which could be removed with a hammer and screwdriver).
I was cycling in relatively civilised countries, USA, Canada, New Zealand, Australia, France, roads were generally good and the worse mechanicals we had were punctures.