<open can of worms>
Fun topic
Ok, my take on this subject.
The trails you run will select the tire size, this will then set if lift is needed or if just resetting the springs is a valid solution. (Upgraded springs can address soooo many issues and even improve ride) The trails will also make the need for lockers or even four wheel drive for you. (importance of wheel base is another topic) Lift is for break-over/clearance or to clear tires. Most lifts don't increase wheel travel, strange as that may sound until you see the long bump stops.
Sadly however some people go crazy on lift to clear their tires. I have parked beside Jeeps with 33's that sit higher than my Jeep on 40's. Center of gravity is important and many people appear to love to load their roof racks with all kinds of heavy things, this can impact the center of gravity more than lift. I am mindful the pack anything with weight as low as possible and consider the upper areas the reserve of light and bulky items.
So the initial starting point is where you want to go and what you need to get there safely and effectively. The statements in this thread are correct in that most targeted ExPo trips are not that hard core for clearance but require durability of suspension. It is the same in Australia, most places people select to visit require only robust tires, then maybe a roo bar, spot lights and long range tanks. (Diesel Toyota's rule in Australia, you can get parts almost anywhere)
The group requirements split for off-road cross country travel. A couple of years ago I ran into the Rover club on a trail on CA highway four, they were having all sorts of trouble on modest trail for most Jeeps (nice group of guys). The true lesson here is that different vehicles suit different applications. A stock Rubicon in the Sierra rocks works very well until you hit real big rocks. A LR3 for a nice gravel road is just joy, and Mogs are fun until you have to dig out a bogged one, then you wish for a Samurai. Then you run into those Toyota pickups turned into tube buggy hybrids. Oops, off topic I think.
Big tires roll over rocks better than little ones, but big tires often break stock things. Standard tires on many vehicles have gotten bigger over the last twenty years, a good example is the new JK which only needs a couple in inches of lift for 35's or a touch more for 37's. Only five years ago this was the realm of hard core, now they are mall crawlers for soccer mums.
How many portal members know the total weight of their rig in full trail prep ? Or the load on each tire ? This is a real eye opener for nearly every one. You may have issues just because of the total weight on the suspension. Now there is a good topic for the Engineers...... mass, spring rates, rebound, up travel, droop it's hurting my head already.
<close my can>