Hey there! Nice to meet you!
Unfortunately, there is no set timeframe for replenishing out‑of‑stock codes, and it may take months or years.
In the meantime, I recommend saving your rewards points and checking the Rewards Store from time to time.
You can also provide your feedback regarding your issue on https://rewards.bing.com/
Click "Feedback" at the bottom right corner of the page > then submit your feedback.
Thank you for your understanding! Please let me know if you need anything else.
Best regards,
Darhyl