I ask this both as a prospective buyer and prospective owner:

How important is it that a Vantage be serviced yearly, even if driven much less than 10,000 miles? Is a car significantly more likely to run into problems if serviced at 10,000 mile intervals? Thanks.

 

The car should be serviced annually regardless of mileage. Fluids degrade over time whether or not the car is driven. Obviously items that only wear with use (e.g. brake pads), won't need replacing as often. Another important factor is resale value - a car with a non-factory spec service history will be harder to sell and will command a lower price.