If the rubber boots are in good shape, the CV joints last a long long time. If a boot is torn, then plan to replace the axle assembly with a reman unit. Some people will try to clean up the joint, regrease it, and replace the boot, but I think that way is a waste of time and effort. Once the boot rips, dirt gets in there, and the CV joint will wear out prematurely.
Symptom of worn out CV joint is clicking sound when you are making a turn. Visual inspection is not possible without removing the boot, and what is the point of that? A little bit of rotational play is not unusual, but if the joint is worn enough to click, time to replace it.
Whoops, I was thinking of the front axles/CV joints. I now see that you were asking about the rear axles. I'm not sure what a worn joint on the rear axle would do. I don't think that it's a common problem, but I just don't know. On my 2003 with 208k miles, the original rear axles seem to be doing just fine.