The frequency at which you should pack wheel bearings depends on several factors, including the type of vehicle, driving conditions, and the type of bearings.

Here are some general guidelines:

1. Passenger Vehicles: For most cars, trucks, and SUVs, wheel bearings should be inspected and possibly repacked every 30,000 miles (48,000 kilometers) or during every second brake service.

2. Trailers: For boat trailers or trailers that see frequent use, bearings should be packed annually. If the trailer is used in water or harsh conditions, you might need to repack them more frequently.

3. Heavy-Duty Vehicles: For heavy-duty trucks or commercial vehicles, it's best to follow the manufacturer's recommendations, which may suggest more frequent maintenance due to higher loads and longer distances.

4. Off-Road Vehicles: If you frequently drive in off-road conditions, mud, or water, you should inspect and repack the wheel bearings more frequently, possibly every 10,000 to 20,000 miles (16,000 to 32,000 kilometers).

Regular maintenance can help prevent bearing failure and extend the life of your vehicle's wheels and axles. Always refer to your vehicle’s owner manual for specific recommendations.