Which is sometimes the case, but often it could be just a leaky seal. It is important that you check for leaks, a good way of doing this is cover the system in soapy water, to make the leak visible. Once you do this you may notice that it is coming from an air line or air bag. If that's the case you will now know what to replace. But if you don't notice any leaks, it could be a very slow seal leak. And if it is your air bag, you can either spend loads on an air suspension system, or you could buy a much cheaper and more reliable air suspension conversion kits.
On an air ride system there are solenoids that go into each air spring. These solenoids are what control the release of air from the air spring. There are a few small seals on these solenoids, that often will be the cause of a leak. If you suspect its these seals try to put some soapy water around them and watch very closely.
It may be leaking to slow to see. But if you cant find a leak anywhere else, it would be a good idea to replace the seals, as seal sets are only about $10-$12 for each solenoid. A slow leak from one of these seals could eventually cause your compressor to go out.
When you replace these seals, the ones that leak are usually the two that between the solenoid and the air spring. But you should also go ahead and replace the seal that goes between the solenoid and the line as well.
That seal is included with most seal kits anyways. It is especially important to replace these seals anytime that you remove the solenoid. As the seals can go out even if the solenoid has not been removed. But once it has been removed they will never seal up right, it will leak every time. For more information, please visit: http://www.airsuspension.com/