CX lifetime was withdrawn 6 or 7 years ago. I think they used to give it for five consecutive years of Diamond membership. Someone who's been around longer than me could confirm.

All they have now is an "Invitation" level (like BA Premier) which is equivalent to Diamond / OneWorld Emerald in status but is totally at their whim. Generally I believe it goes to top managers in companies that have a large amount of travel spending that can be directed towards CX.