To my knowledge, mIRC only checks to see if the registration information is valid. I don't believe the IP address and time are checked/recorded for this purpose. It makes sense that this is the case, as I have had several different IP addresses, due to different IP providers as well as the fact that the addresses are dynamic, and mIRC has only checked the registration site once since I installed mIRC.
mIRC only checks the registration information due to the number of key generators and/or fake keys that have shown up.