Testing Paypal subscription IPN

I'd like to test paypal subscription IPNs, both the ones received when a subscription is created, and the ones sent later with the next payment (such as monthly if the subscription is $x per month).

However I'd prefer not to wait a month or a day to receive the second IPN. Is there a way to have an IPN sent quicker, such as hourly, using paypal or their sandbox?

On the documentation it says you can only specify years, months, days, and weeks as the subscription period.