Wish I'd known this before purchasing and getting my client to buy as well. I thought that I can save these credits and use them in bulk once / a month or so. I really can't do much with 1200 credits, or my client on tier 5 with his 4k or whatever, I thought it could stack.

This should be explained better on this page, as this is not worth it for me then

Any way to get a refund?
I also need to check with my client if he wants it too.
Really was happy about saving credits and using when needed, but this is useless, we'll just waste a lot of credits, and I don't want to have to clean every day. Too much hassle for busy people

Dear Sergio67, the system is designed in that way so that we could maintain the service quality in the long run. Every email validation batch costs us money. So it would be impossible to provide good quality service in the long term with stackable daily credits. That's why the credit system is designed in that way.
About the refund, you are fully protected with 60 days refund policy. Just go to the products section of AppSumo and press the refund button there. Your money will be back to your account soon after that. Thanks.