Most of us drive our classics cars less than 5000 miles per year. Some of us drive them less than 2000 miles per year. So 30,000 mile service intervals make no sense.
Condensation contaminates the oil in the engine, gearbox and axle. Brake fluid absorbs moisture from the air. Coolant loses it's anti-corrosive properties with the passage of time. Rubber suspension bushings and drive train mounts deteriorate with contact with the air (or worse - oil leaking from drive train parts). These are the reasons why annual inspections are so important for infrequently driven cars.
Get your car ready for the driving season.