On the truck is only about 25% of the time. But if you want to say miles, over the last 5 years I have had the camper on the truck for 57% the 18k annual miles. Since July when my daughter gave me back the car I gave her 6 years ago, I've haven't been driving the truck as my daily driver so have been averaging about 98% of the miles with the camper on.
While I've only used 4wd with the camper on board a dozen times, I use it almost every time I go camping on a long trip. There is no way I could get the front of the truck up on my 10" block with only a 16" long board if I didn't have 4wd to let the front wheels pull themselves up. At some campsites I've had to stack lego blocks on top of the boards sitting on top of the 10" blocks for a total gain of 16" which would be impossible without 4lo. Without 4wd the boards/blocks would just be pushed out from under the tires.
When I bought my first truck 25 years ago, I knew the advantage of 4wd as I had grown up on a farm. However, I wasn't looking for a truck but came across when the suburban wouldn't tow my 7k trailer just happen to have 4wd. Convinced the wife it would do the job well and had the crew cab for the kids (not very common back in the early 90s). On our first long trip with the rig, we left about 5am in the pouring down rain so the kids would sleep, I missed the turn and found a nice paved parking lot to turn around in. Only problem was it was red clay and slick as get out. Almost made it in 2wd until the front dropped in a 6" ditch. Fortunately, 4wd allowed me to back out of the ditch, finish turning around and be on my way without even getting soaked by getting out. A few miles down the road after my nerves calmed down I looked at my wife and said the 4wd was already paid off to which she agreed. Since then, I've bought two new trucks. On the first one I was trying to get the price down so offered to drop the 4wd to which my wife responded that I shouldn't even worry about buying the truck if I don't get 4wd.
