My Z4MC has just over 6,000 miles to go to its first oil service (apart from the 1200 mile inspection which was done). However, it's also coming up on a year old. Is there any time-based element to the servicing, or do I just go by the OBC? Before condition-based servicing, service intervals used to be like "12,000 miles or 12 months". So do I need to book her in for a service soon-ish, or can I wait until the remaining 6,000 miles are done (which will probably be another 9 months or so)?