The frequency of checking the belts in your car can vary depending on the make and model of your vehicle, as well as the specific recommendations provided in the owner's manual. However, as a general guideline, it is recommended to inspect the belts during regular maintenance intervals or every 6 to 12 months.

Here are some signs that indicate it's time to check the belts:

1. Mileage or Time Intervals: Follow the manufacturer's recommended maintenance schedule for your vehicle. This information is typically outlined in the owner's manual and provides guidelines for when specific components, including belts, should be inspected or replaced.

2. Visual Inspection: Regularly inspect the belts for signs of wear, damage, cracks, fraying, or glazing. Look for any signs of excessive looseness or tightness. If you notice any issues, it's advisable to have the belts inspected and replaced if necessary.

3. Squealing or Squeaking Noises: If you hear unusual squealing or squeaking noises coming from the engine area, it could be an indication of a worn or loose belt. The noise is often more noticeable during engine startup or when using certain accessories like the air conditioning system.

4. Glazing or Shiny Appearance: A glazed or shiny appearance on the belt surface can indicate belt slippage, which reduces its effectiveness and may lead to premature wear. If you notice glazing, it's advisable to have the belt inspected and replaced if needed.

5. Loss of Belt Tension: Belts can become loose over time due to stretching or normal wear. If you notice that a belt is loose or has excessive play when gently pressed, it may need adjustment or replacement.

6. Age of the Belts: Even if the belts appear to be in good condition, it's important to consider their age. Most belts have a recommended lifespan, typically around 3 to 5 years, after which they should be replaced as a preventive measure.

It's worth noting that some newer vehicles have a serpentine belt that drives multiple components, including the alternator, power steering pump, and air conditioning compressor. If this belt fails, it can cause multiple systems to stop working. Therefore, it's crucial to inspect and maintain these belts according to the manufacturer's recommendations.

In any case, always consult your vehicle's owner manual or contact a qualified mechanic for specific guidance on checking and replacing the belts in your car.