I'm always on dirt, always on bumpy hillside/uneven terrain, almost always carrying near max loads of rocks and wood - probably 75% of the time. So, I haven't taken it out of 4WD for close to a year now. I like the "extra" feel. It feels safer, rather than waiting until it feels like I need it.
I keep the U-Joints lubed. But is this not good? If I don't really need 4WD, should I make a point of disengaging it?