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.

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.