No, it is not possible to accumulate bundle choices. If you don't use them in 30 days, they'll be automatically exchanged for a bundle you don't own, according to which plan you are subscribed to:
- Flex plans: If no choice is made within the 30-day selection window, you will receive the current bundle of the month for your theme (Fantasy and/or Sci-Fi).
- Premium plans: If no choice is made within the 30-day selection window, you will receive the most recent bundle you don’t own for your theme (Fantasy or Sci-Fi).