G'day,
Driving a part time 4x4 in high or low range on hard ground should not worry the axles but it can cause the transfer case to bind up - and then expensive things break. You will feel the transfer case binding up if you are going very slowly. If you are going quickly things will break.
Using 4x4 low in a Navara, or Colorado or my Rodeo is OK for launch and retrieve provided that you keep power as low as possible just to overcome the obstacle and then stop, engage reverse and roll back a couple of inches and then disengage low range and 4WD.
As much as I like the control of manual transmissions I have had automatics since asbestos was banned from automotive friction materials and engines got a lot more torque. Clutches just can't stand the torque of engines and towing any more.
Having said that, I cannot understand why makers of 4x4 utilities won't fit a centre differential in the interests of safety. They add airbags and ABS brakes and more power and torque but not the best power control and safety system they have to offer. For example, Toyota could put the Prado driveline in HiLux pretty easily. I think the Navara cousin, the Pathfinder has a centre diff. Isuzu (aka) Holden Rodeo/Colorado had a constant 4x4 in the Jackaroo Monterey 15 years ago. Land Rover made all their vehicles constant 4WD in the mid-1980's. Why can't we have what we need?
Regards,
White Pointer