Pingomatic throttle limits

Hello,

Note: this question is not about WordPress, but I didn’t found a better place to ask it, sorry.

My company recently started to use Ping-o-Matic service to notify external services about our users activity. We send GET requests directly to https://pingomatic.com. Quite often we get a throttle response, even with simple limits in place. What is your throttle limit? May it be increased? Is there a better way to use this service?

Thanks in advance.