This is what I received from the GS response team. It seems reasonable.
The Elite membership is not valid for Life. Elite is a membership tier (not a separate membership with a separate #). The system prints the expire date for your membership #, which is a Life membership that is valid for Life. You were upgraded to the Elite benefit level for 3 years.
The membership #s are purposefully the same. The Elite benefit level takes precedence until it expires 12/31/15. Life memberships do not expire so you have nothing to worry about there.
If for any reason, after 12/31/15, you have any issue we are here to get it resolved immediately. But, I assure you that will not be the case as a Life membership does not expire.