RPG52,
From my years of owning both Chevy's and GMC's currently a 83 and 87 one of both. along with Jeeps,the CV joint on the transfer case end of the front propeller shaft gets chassis lube twice per year. Spring and fall. I live in snow country, and run in 4x4 at least once per month during the winter months. I have traveled 600 miles in one shot in 4x travelling 60-65 MPH.
The 87 has 65K miles and the 83 close to 280K.
I have not replaced a CV joint yet. If you can see clean/fresh grease where the ball is you should be fine. If not. insert the needle, pump in some new, until its visable at the ball end.
I've have wheel bearings fail in front do to water contamination. Now I clean and repack every 30K miles or 3 years. (Hubs, spindles, cross joints, and wheel bearings).