The front Air Bags can come loose from the top mounting.  The seal can easily be broken when the wheels have been allowed to hang down without disabling the air suspension system.  This can be an intermittent leak when stationary as the weight of your Range Rover will tend to re-seal them, but when driving, both movement and heat will allow air to escape from between the two.   

Front and rear Air Bags have had leaking 'O' Ring seals at the Air Pipe connection and the Air Bags can develop small age cracks that the air bleeds out through.  (8 to 10 years seems to be a good age for the Air Bags to develop these small cracks, even earlier if your Range Rover has been used in hot climates.) 
Replace the Air Bags when the small cracks appear.  (The rubber bellows are available separately.)

The Valve Block has been known to leak from the 'O' Ring Seals for the Air Pipes, from under the Solenoid covers, and internally.  Replace the Valve Block.   (Reconditioned Valve Blocks may be available from your repairer) 

A leaking Engine Exhaust Pipe Flange over the top of the of the rear axle directs the hot exhaust gasses on to the three Air Pipes located on top of the chassis and melts them.  (Air Pipe joiners are available.)

A Battery Acid spill in a Range Rover will eat away the Air Pipe under the Battery tray.  (RH front Air Bag)

Air Tank leaks have been found at the 'O' Ring seals for the Air Pipe and at the threaded connections. 

It is strongly recommended that your Range Rover be thoroughly checked for air leaks regularly and before you depart for the Outback.  The extra work the Compressor and the Valve Block have to do to keep up with air leaks only shortens their working life and costs you money.