I drive my IS 250 way below average because I use public transportation for my work commute. I would like to take my car in based on mileage, but Lexus recommends a check up based on mileage or months - whichever comes first though. If you don't drive the car as much, do you think it's important to get service based on months driven? For example, my next scheduled maintenance should be the 12 months or 10,000 miles. Right now, I'm at 6k miles but at 18 months. No signs of any problems.