Are they reliable? Has been for me. Only let me down once when the front prop shaft CV failed, a double cardan shaft will sort that.
Are they capable off-road? Quadradrive II is! The most limiting factor is ground clearance. A 2" lift lets you fit 265/70/17 under the guards, 2.5 to 3" gets you 255/75/17"s (32"). You may be able to get 33's with a 3" lift but front CVs will be at there limits. A 4" Super Lift will set you back about $4k
https://www.ebay.com.au/itm/2005-200...53.m1438.l2649
Long journeys? Average holiday is 3 week's and 5000km's for me and I enjoy every moment I'm in the Jeep. I have only a 2" lift so I can't comment on the reliability or ride quality of a SuperLifted WH.
This is on-board my jeep with the Sydney Jeep Club
https://youtu.be/OOzPfEjvvtk & https://youtu.be/T7-SVD1fSDM with only 31" road tyres.