I replaced the seals and regreased the insides of my rear suspension (DT Swiss SSD 225 air shock) yesterday. Fantastic shock by the way. Not a hint of dirt or wear inside. This is the first time I have serviced the thing in 7000km.
The Lizzard Skin suspension boots have played a large role in this I think. They keep all the dust, water, and dirt off the shocks, so wear on the seals is decreased.
It is very easy to take this shock apart. Put the end in a spanner, and then just screw the housing off with your hand (make sure the air is totally removed before taking it apart!)