The date in which your photo credits expire depends on whether your plan includes or does not include rollover credits. You can find out whether your plan includes rollover credits here.
If your plan does not include rollover credits, this means any unused credits at the end of each credits cycle will expire, and not carry over into the following credits cycle. For this reason, we cannot extend expired credits. You can read more about your credits cycle here.
If your plan includes rollover credits, this means any unused credits will roll over from one credits cycle to the next. Any accumulated credits will only expire at the end of your contract cycle.
Find out how many image credits you have available here.