The time will vary because there are several processes involved discovering and updating elements automatically within Iris. 

On a default installation, this process should not take any longer than 3 hours. 

Keep in mind that if a mnemonic was manually changed, like changing or added VRF information or IP address, these mnemonics will be marked at Manual and they will be skipped by the automatic updates.

It should take between 10 and 30 minutes for graphs and mnemonics of the newly added devices to start appearing in the front-end.