Joe replied:

John,

CV joints pop when they are subjected to too much stress. This is often when (say) a locker has been fitted to the diff and forces both CV joints to turn at the same speed, imposing atress on the CV joint when the tyre can't easily slip to accommodate it.

You didn't say anything about a diff lock, but only the suspension upgrade. Well body lifts impose their own stresses on the CV joints of independently suspended front ends like the Prado by making the angle that the CV joint works at more acute. Have you had a body lift?

What else? Well it is possible that the rubber boot over the CV joint might have been torn allowing the dust and dirt to get into the joint and promote some rapid wear.

Of course, if you were travelling over particularly rocky country you might also have overstressed the joint(s), but this is not likely.

Other than that I have little to suggest, but I wish you luck.

BTW - the load being carried should not affect the CV joints as the loads are carried by the suspension systems. It would come into play if you were belting the joints into rocks etc, but not otherwise.

Joe