You never know. If you have a clearance a bit off, if you got just one very heavy gear loading and lifted a tiny portion of a gear face, that's all it takes to begin a downward spiral. Opening them up, reshimming & resealing is not a bad idea, compared to what broken gears, shafts and cases cost.
Refresh intervals are relative to how much power and how you use them. On a time vs. power chart, the curve wouldn't be a straight line. In other words, you don't get half the hours at 1200 hp that you would have with 600. Not a straight-line relationship. Compound that with the 3rd dimension of those unknowns like the occasional bad landing or the holeshot here & there and you complicate things even more.
100 hrs is a good interval for a non-raceboat.