Rust:In the end...
Nothing can permanently kill a LandRover except for rust. Frames are terribly susceptible to rust, but they can be replaced. Firewalls and miscellaneous bits and pieces are now often the problem. Remember, unless you live in a dry climate like Arizona or have a perfect Rover, this is a battle you will have to face.
STOP IT!
There are many types of rust-converters that are available for purchase. Paint them on and the rust chemically changes into an inert form of iron that can be painted over. This stuff works great and definitely gets OldRover.Com's great product award! Paint it here and there and put the rust into hibernation for a year! Most of the time I won't even actual put real paint on top. The only drawback is the black color but your Rover is tough.Though many types exist, I suggest a brand made by Mar-Hyde (SP??). The name escapes me but it comes in a cardboard box and has a white thick milky consistency. Another type called RustMort that is clear does not seem to work anywhere near as well. Good luck and God speed!