W109 self-leveling air suspension: the defining ownership concern

The hydropneumatic air suspension on 300SEL (2.8/3.5/4.5/6.3) W109 cars is the single most-discussed worry, but the thread splits between fear and reassurance. Skeptics cite scarce parts and, more critically, retired specialists; experienced hands counter that with routine use and maintenance the system is durable, and buyers commonly ask how long a parked car holds air (answers range from ~18 hours to a couple of days) as a health check.