If I cancel, will I lose my credits?

If you should cancel your subscription, you will retain your monthly credits until your renewal date. When they will disappear. 

To provide and example, lets say you subscribe on the 10th of January, then you cancel on the 11th. You will keep your monthly credits until the 10th of February.

Credits that you purchase directly will never expire. 

These Purchased Credits are displayed separately, from your Monthly Credits in the top right drop down when logged in.