A little suggestion to throw something else into the mix. Consider Delta's SkyMiles program. You can keep flying KE but just credit your miles to Delta. Silver Medallion status comes at 25,000 qualifying miles. That gets you added to the list for unlimited complimentary domestic upgrades. (Actually getting them is a function of your Medallion status and the fare class your ticket is booked in; Silvers do get upgrades sometimes, and if you're flexible you can pick flights that will improve your chances.) Silver also gets you a 25% redeemable mileage bonus on every SkyTeam flight. Gold comes at 50,000 miles and, crucially, comes with a 100% mileage bonus. That makes mileage-earning go much faster. Platinum (SkyTeam Elite Plus) is at 75,000 MQM's; it also has the 100% mileage bonus and some other benefits, notably lounge access for international travel in Economy.

The best part of Delta's program for you would be using it for travel beyond Korea. Instead of just taking an award trip to Korea, go someplace else like Thailand or Hong Kong or Singapore, whatever, and book a long "stopover" in Korea either going over or coming back. That gets you a free trip to wherever else you decide to go because awards US-Korea are at the same levels as US-Southeast Asia. If you just want a side trip on an award ticket, you can book ICN-Southeast Asia for 25,000 in Economy or just 30,000 in Business-- one of the best deals around and a lot cheaper than SkyPass redemptions for the same routes.

The drawback of SkyMiles for you is that you have to requalify for Medallion status each year. Taking one of your trips home as an award ticket could make that tough. Also, Korean Air imposes blackout dates for US-Korea award tickets booked through Delta. The last major drawback is that KE will not deposit any miles into a partner's program for tickets booked on the Q fare basis (commonly sold by travel agencies, these are the cheap fares that earn 70% mileage in SkyPass).