This is called ‘rationalization’. 
I know a guy who pedals around with only one leg. His cranks never break. Or, they haven’t yet. I don’t think Mark was more imbalanced than that.
Your point about exposing the cranks to humid conditions is valid, for sure. I bet also if you get them wet and then ride them around in freezing weather it’s a big issue as well. I’ve known people to try various tricks like clear nail polish or silicon sealant along the seams to keep the water out. That’s intuitive…don’t know if it works.
Couple points…I’m not willing to spend >$100 on equipment that’s good for ~two years…and, second, are there any other brand cranks in your area that failed? I’m at 7, I think, not counting non-drive-side crank arms that fall off. A lot of times the non-drive-side crank arm falling off is related to user error. Drive side crank spider blowing apart is not user error.
My own personal bias is that, unless you smash it on a rock or a curb, no crank should fail ever. Except for the bearings. I’d never heard of a crank failing before Shimano hollowtech. Hollowtech is incredible technology but those cranks have a fatal design flaw.