We should ask the (still existing) Invitation members for the definitive answer - I think a couple post here occasionally. I don't have any record, but from memory I think it was something like 1M flight miles on CX, where J counted as 1.5 times and F as 2 times. Back in those days that was quite a lot. With the increase in CX's network and the amount people fly I can see that lifetime would have to be much more than that these days.