You should update your local product inventory feed daily.

• Quarterly
• Monthly
• Weekly
• Daily

The correct answer is: Daily

Explanation: For the best user experience and accurate representation of in-store availability and pricing, it’s essential to upload your local products inventory feed at least once a day. While daily updates are the minimum, the flexibility exists to submit updates multiple times a day for specific segments of your inventory.

Read more here: https://support.google.com/merchants/answer/7371791