This module will expire any rewards customers got in your store.
Just install it, set for how long rewards are valid and let it work in the background.

Demo
https://ggwshop.com/oc3038/admin/index.php?route=extension/module/ggw_rewards_expiration
User: rewards
Pass: rewards


Features:
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For every Customer Group rewards expiration setting in days.
For every Customer rewards expiration setting in days.
No rewards expiration per Customer Group setting.
No rewards expiration per Customer setting.
Points older than the set time-frame will also be expired.

Individual Customer setting has priority over the group setting.

Example:
Customer A is in the default customer group.
This group has a rewards expiration setting of 365 days. Customer A has setting of 0.
So A's points will remain valid indefinitely while for other customers points will expire in 1 year after they earned them.

The module works best with a cron job setup but is not required.

Get a License here:
https://www.opencart.com/index.php?route=marketplace/extension/info&extension_id=43705