Long Cranks and Hub/Axle Failures

Has anybody found a correlation between crank length and hub/axle failures?

After putting the new hub on the 40" big wheel, Tommy at TUF said to be sure to put 5 1/2" cranks on as anything bigger than 6" increased the incidence of failure. I realize that a custom big wheel hub is not a common item but it got me thinking and that makes my brain hurt.

I would think that for doing drops longer cranks could lead to earlier failures. Has anybody had problems in other riding situations? How about the standard Coker hub?