THE SHORT ANSWER
There is no single detailing schedule for every car. Base the timing on how quickly the interior and exterior get dirty, where the vehicle is parked, and the care instructions for its finishes. Review the routine as use changes.
Look at use before mileage.
A short daily school run can bring more interior mess than a longer solo commute. Pets, food, work equipment, and outdoor activities change the picture. Pay attention to which areas build up first instead of choosing a service based only on the odometer.
Parking affects exterior care.
An uncovered vehicle may see more deposits and weather exposure than a garaged one. Avoid letting contamination sit simply because the next planned appointment is weeks away. Follow finish-specific guidance when handling fresh deposits and avoid rubbing dry grit into paint.
Separate upkeep from a reset.
Routine washing and light cabin cleaning help maintain a baseline. A more involved detail is useful when the condition exceeds that routine. If every visit turns into a major cleanup, discuss a different frequency or focus.
Let the plan change.
New pets, a longer commute, different parking, or a family trip can change what is useful. Reassess the car rather than renewing a schedule automatically. Ask for the smallest service that addresses the current condition.