Then when the levels were up'ed 25/50/75 and the titles changed from Bronze/Silver/Gold to Silver/Gold/Platinum - the Infinite cards were recharacterized as Platinum Infinite. Remember the top level used to be 60K EQM - so having keep the Infinite level at Gold would have been a downgrade. You had to really earn the level. Being upgraded in a year because you were close, did not count. You neded 5 consecutive years of exceeding the top level requirements.
And we have Randy to thank for convincing CO to give Infinite elite "platinum" status. I understand that they wanted to give lifetime gold (mid level) but he got them to go all the way. It was the right thing to do - but CO didn't have to do it.
Now if they had only grandfathered those old mileage awards!