I tried Affirm (https://www.affirm.com/) -- I missed one payment because of a bad check from my employer and I was barred from the service permanently. Even though only a week went by between payments, and I payed off all of my loans as soon as I got paid.
Seems like it's clearly spelled out in their FAQs:
Q: Do I have a credit limit with Affirm?
A: Unlike a credit card, Affirm is not a revolving line of credit. While customers can take out multiple Affirm loans at once, each Affirm loan application is evaluated separately as a closed-end transaction. An application from a returning customer may be denied, however, if that customer has failed to repay other Affirm loans on time or if the customer shows excessive borrowing behavior.
