just an idea for this: drill durability as everything breaks down in time, especially if that thing is mechanical or does a high power stuff; the excavator and laser drill should also get some life expectancy (or was that drill life you wrote first?) ..if yes, then how about drill cycles? setting up a cycle to run in the next xx minutes/hours/days/etc then shut down and how about automated drills? more/less effective than manned.. er, I mean Kerballed drills, but as a trade off to either be lighter/heavier in mass, or work faster/slower, use less/more energy... just to balance things out...