...even when they do fail the nut holds them on the axle...
No they don't.
The hole in the middle of the outer race is bigger than the nut.
Once the bearing has collapsed, the pedal body, complete with outer race, will slide over the spindle, complete with nut and inner race.
...so it's just a question of replacing the cartridge bearings when they start to get some play.
Except that I have found the time between the bearings feeling or sounding worn to them failing completely can be less than half an hour.
Despite my criticisms, I still use them, but with the following provisions.
Having broken two egg beater spindles, I now use ward Industries titanium spindles which have got a 235lb rider weight limit.
Ignore Crank Brothers'/2pure's advice on bearings. Remove the rubber seals and purge the bearings with grease far more often than the recommended 100 hour interval.