What is the difference between Felt credits and subscriptions?

Subscriptions are a monthly membership that rewards you with a huge discount if you use any of your 3 free subscription cards that month. That’s right! Each month, you receive 3 free cards with up to 4 frames each (a value of up to $21.00)! CAVEAT! The subscription cards don’t roll over each month; you can only roll over the dollar equivalent to your subscription cost if none are used.  Credits, on the other hand, are a simple way to receive a discount when ordering a large number of cards, and they never expire.