Steve, about 4 weeks ago I was faced with the same situation. Mind you I was looking at changing the airbags for the 4th time at 81 000 km. I ended up opting to import some new bags from an outfit called strutmasters because they cost 1/2 of what the local dealer was asking and they came with a limited lifetime warranty vs LR 12 month warranty I Also redid the suspension and replaced all the shocks with Bilisteins hoping to reduce the rear travel.
In the end the way I looked at it was that when we bought the Disco II, the ace suspension was a 4000$ (CAD) upgrade. It seemed silly to be spending more money on getting rid of an unreliable feature. I figured I would give it one more try before I drive my truck into a brick wall.
So far all seems good. The new bags are holding and the Billisteins feel rock solid.