And to be clear, it's not a policy, it's the law. Air carriers must either give you a 24-hour cancellation or a 24-hour hold before purchase. UA uses the former. I've found my refunds on simple tickets (entire purchase with one CC) to be processed within 2 bus. days and show up as a pending credit in that time frame.

Nonetheless, I keep a screen shot of everything until I see the refund. And, I don't wait until 23:59 to try it.