Are there any limits on the number of requests per day? How often can I send requests?

There are no limits on how many requests you can send — you can trigger them as often as needed.

The only limitation applies to workers receiving requests:
​a worker cannot receive a new request until 5 minutes have passed since the previous one, because the system gives them time to respond.

If you send another request earlier, it simply won’t be delivered until the 5-minute window expires.