Rendering should not take any longer with additional LightMix channels UNLESS you are running out of RAM (since more channels require more RAM). This one would need to start as a bug report so we can investigate what is going on for you - can you send in a ticket via https://support.chaos.com/requests/new . As an Idea, I will have to set this as Declined (it can be reposted as an idea if it turns out not to be running out of RAM or some other bug). Best regards.
Rendering should not take any longer with additional LightMix channels UNLESS you are running out of RAM (since more channels require more RAM). This one would need to start as a bug report so we can investigate what is going on for you - can you send in a ticket via https://support.chaos.com/requests/new . As an Idea, I will have to set this as Declined (it can be reposted as an idea if it turns out not to be running out of RAM or some other bug). Best regards.