You could also go for Flying Blue (Air France, KLM and some other airlines).
With Flying Blue you need 70k per year on any Skyteam airline to reach Platinum status (= Skyteam elite plus).
After 10 consecutive years with Platinum status you get status for life.
Whether this makes sense for you depends on the booking classes you typically fly with. Flying Blue gives you less miles for low Economy classes than Delta does. On the other hand, I think that KE is meaner when it comes to the amount of miles you get. So you should consider Flying Blue an option.