I personally run an OME setup for almost 2 inches of lift. Any more than 2 inches of lift and you may very well have to replace a lot of other parts as well. Driveshafts, would just be one of the many upgrades required to run more than 2 inches.
It could very well be the difference between the cost of spring (around $400) and $2500 for all the required items to upgrade 3 or more inches.
Joey's right - don't go over 2" inches of lift (approx.) or you start running into all manner of parts replacement issues and those, in turn, lead to stability/driveability concerns on the highway. Besides, 2" looks real good without that silly 'Monster Truck' mega-useless-boost look. The number one issue that will keep you out trouble from high-centering or hitting stuff underneath when off-road is the fact that your Landy has a relatively short wheel-base; case in point: nearly all the best roads for 4X4 fun up here in BC are old logging roads that can lead you miles into spectacular terrain. But in order to prevent idiots from killing themselves (which they routinely do anyway) - the forrestry companies 'decommission' the roads when they stop using them. This means they dig some earth out of the road (i.e., across its width) crating a ditch and then they build about a three to four foot high mound/berm with that earth. Inevitably guys in their big-rig fords and chevys attempt to get over those and just as inevitably they get stuck on the top (i.e., high-centered) as their wheel base, regardless of six inch lifts - is just too long and they end up looking like a seesaw (its all very embarrassing for them - especially when some turkey [such as yours truly] comes putting along in his tiny SJ410 or Landy and easily clears the decommisioning berms - and all with nothing more than factory lift)!
For general off-roading, the most critical issue of all is - how low are your diffs? Because that's what's going to hit something first - and you can have a 12" lift without moving your diffs up a single inch!
2 inches of lift will permit you to put on a reasonably larger tire and that, in turn, will also give your diffs a nice lift too - and all without truly affecting your Landy's highway speed stability, etc. Also, diff protectors (or 'pumpkin hats') are a good idea for the more rambunctious off-roader. I have never had a need for them but, then again, I like to baby my Disco - even off road - which means - I slow right down on the rough stuff!
