I have been playing this exact game for years. Since DL's award redemptions are so miserly, I have avoided them. UA/CO USED to be great snce you could earn 100% RDM bonus as Premier Exec / Plat and then redeem on Star, but since UA has cut the RDM bonus, I see ZERO value to use UA as a back-up program.

What I have done, is to get the MP Club Card which gives you 1.5 miles for every dollar purchase, and the Chase Sapphire Preferred which gives you 2x on travel and dining and access to Ultimate Rewards Shopping Mall.

While I will still qualify for Gold this year (through 1/14), I will no longer fly UA next year and simply accrue miles and redeem on partner Star Alliance airlines. That way, I don't have to fly this miserable airline, but still have access to the terrific award availability on partners.