There are many merchants who have found that increasing the generosity of their refund policy leads to decreased refund rates.
I.e. a 6 month refund window may have a lower overall refund rate than a 1 month window.
It gives users who are on the fence about the value of a product more time to see how they've gotten value out of it. It also gives people longer to forget to ask for the refund.
The only reason some companies have a "1 year" refund policy instead of "lifetime/anytime" is because of issues like credit card merchant processors being uncomfortable with the credit risk that creates.
I sell 5-24 hour long online courses. A two week trial would let someone see everything, and would leave the user with no reason to purchase.
This is why I haven't done full free trial yet. Because 2-3 days seems short. But I'm wondering if it counterintuively might be optimal, by removing friction to trying the course.