I do lock in my 4x4 for the occasional snow fall here in the Pacific Northwest.
However, I have used it more for helping others on boat ramps , stuck in mud etc.
The place I use it most is when I get to the campground.
Setting it into 4Low it will just walk it's self nicely at idle slow and steady as I steer.
I have both manual locking and on the fly (dashboard control) hubs.
I have disconnected the hoses (at the pump) for the on-the-fly switching so the front wheels are not locked when I use 4x4 for maneuvering the 5th wheel.
I learned the hard way about backing my 5th wheel up the slope of my driveway. When the transmission is put under heavy pressure, like backing a heavy trailer up a slope, that pressure has to go somewhere... there usually is a small vent/valve on the top of the auto-transmission...when the extreme pressure and heat is built up... tranny oil will spray out of this vent leaving you with a mess and thinking you just blew your transmission.
That's when I was told by a Transmission expert to use 4x4 low to back up the rig, especially up any hills
Yes, a 4x4 truck is more expensive but it is very useful and gives peace of mind when towing.
'07 WildCat 30 RLBS ~ West Coast Edition ~
Trail Air - Tri Glide Pin Box
2000 F350 DRW 7.3 Diesel Lariat 89k miles
Edge programmer, 4" SS exhaust turbo/back
Vancouver Island, B.C., Canada