That dusty old filter is mostlikely in front of the evap coils and helps to keep the coils, fan and ducts cleaner. Without that filter, everything behind it would have the same amount of dust inside it. Dust coatiing the coils will decrease the efficiency of the entire unit and reduce total airflow. A lot of dust could possibly, clog the coils completely. I don't own a Starcool, but I'm pretty sure you could remove the filter and blow it out, or perhaps better yet simply get a home furnace filter, cut it to size and install after vaccuming everything out. Other than an occasional cleaning, I'm not aware of any other routine maintenance needed, but if there is something, I'm sure someone will chime in.
Agile Ride improvement package