How does one know when it's time to replace the center drive shaft CV joint / U joint?

I have this vibration / humming / whirring that comes from the bottom of the car. The sound was traced back to the rear part of the transmission. Various bearings were replaced, but the problem persists. Here is my 1st post about the problem...

https://www.audiforums.com/forum/sho...d.php?t=137539

Thanks for the help!