My BJ73 is due for mandatory technical inspection (TÜV). Need to replace the brake discs and pads. And while I'm in it, I'll go for a complete knuckle job

.
First time for me... Let's get started.
(I may come back to you guys for some advice... And it may take me several evenings.. )
Mission aborted, by now.
Got the wheels off and inspected brakes and knuckels. Rotors are still good, even surface, with little wear in thickness and still well within spec. So are the pads.
Knuckels have no play, neither in swiffel bearings nor wheel bearings. Looked worse from outside than it actually is.
Seals on the back at the knuckel balls do not let significant amount of grease go, and grease is not much diluted and by no means dripping yet. Diff oil shows traces of black MoS2 greas, though (I had an issue here over 1.5 years ago, but apparently got that fixed by cleaning the diff breather. No issues since).
No obvious need to digg into this right now

. Don't fix what's not broken...
But here are some question:
At what intervals would I need to take it apart for in-depth inspection and maintenance?
The truck is with me for 2 years now / 12000km. No idea what the PO did.
Are there any telltales indicating the bearings or bushes are about to die?
Is periodic re-greasing through the filler hole enough of a maintenance?
I thought I would do the knuckle job once either the seal fails and oil-greas significantly leaks out, or the rotors need replacement, or anything breaks / gives issues. Is that a good plan?
Thanks for advice Ralf