Spec up springs that suit your needs, I went for HD springs years ago without really thinking about it, HD usually means that when fitted in normal use situations you will end up getting longer life from it because it was designed with heavy duty use in mind. Springs however need more thought than this, it's not as much that the spring is heavy duty in the sense it will last longer I would argue, it just means they are just designed for heavy duty use, as in heavy loads and towing.
Where am I going with this you say, well, my mainly on road Defender 90 with HD springs with usually just a driver is a bit of a bone shaker on our potholed, poorly repaired roads. Load it up with half a ton in the back and she is a different car, and not for the worse, the ride is so much smoother.
In my situation I really need normal duty springs, and then have a better ride for 90% of it's use, and when it comes to the half ton in the back, well so be it, it won't be as well set up for this scenario as it is just now, but it will still be well within LR parameters and work just fine, all be it doing that all the time it would wear the springs much quicker.
So, what we need to do is swap our springs! Shame your so far away.