There’s a more straight forward way to achieve this. It looks like you’re on a Professional subscription so here’s what you could do:
Create a workflow to enroll your customers – presumably companies, so you would create a company-based workflow.
Use the “Create record” workflow action to create a deal with your desired parameters (amount, close date, assignee etc).
In other words, you wouldn’t be creating one deal and duplicate it. You would tell a workflow which pattern to follow when creating the deal 1.500 times.