Full time 4WD here! First off I don't have any paved surface within two miles of my place and second, it's all hilly terrain. Some roads are not often used and are covered with grass, some dirt/stone and most exceed 15 degree slope. In 2WD the rears slide on either and I'm not fond of that sensation!
I run gear oil, not hydraulic fluid in the front axle and every 20 hours I hit both zerk fittings on the front differential.
4WD is all about the terrain and surfaces you work with, some gotta have it, some don't except in specific situations.