Do my credits or funds expire?

Deposited funds and top-up credits don't expire, and they're refundable to your original payment method. Promo and coupon codes can carry an expiry date, but that's a deadline for redeeming the code, not for spending the credit. Once you redeem a code, its value becomes ordinary project balance and doesn't expire. Individual promotions can set their own terms, so it's worth checking whatever came with your code.