From experience, these cars need maybe a bit more attention than any other car I have owned if you plan on letting them sit for a while. Here's what my experiences taught me.
They have quite a few parts that degrade more quickly due to age. If at all possible, make sure you fire it up once a week and at least drive it around the block. The ABS equipped models especially, because using the brakes helps keep the system working properly.
In addition, some of the electronic parts and sensors don't handle sitting so well either, apparently. Connections and soldered parts can corrode from the moisture in the air, in a car you're not opening or using the climate control in for months, nature will take its course moreso than when it's being driven regularly. Not to mention the air bags in the back for the auto-leveling suspension (expensive).
Wipe down the interior with protectant a couple times a month! Dashes crack, so do leather seats. Replacements in any color are now hard to find. Anything vinyl or leather should be maintained! Make sure the sunroof drains are in good order, you'll have a wet, stinky and damaging surprise.
Hope this helps! If you get one of these that has sat for a while, make sure all fluids are good, check the brakes, check plugs and wires, and makec sure all essential things are in working order.