I HAD those zerks 2 RV's ago and never used them...
I will tear down the components at the beginning of each year to visually inspect. If the outter bearings or shaft look questionable, I will tear down into the inners and re do the seals as well.. For normal wear, I will repack each assembly probably every 2 years.
disclaimer - - I am not a full timer, we are just weekend warriors , last year we only took 4 trips for a total RV rolling miles of about 3500 miles total.the truck did 5000 miles total last year