Too many years ago, in my first job after college, I was a CPA/Auditor for a national CPA firm. Most of the NYStock Exchange Companies I remember working on have either merged or DISAPPEARED. Later on I worked for another CPA firm, Arthur Andersen, which unfortunately also recently DISAPPEARED. Reality is that UAL could soon join the likes of PanAm, Eastern, Braniff, PeoplesExpress, etc, etc.
The few UAL miles I ever had were used years ago. Were I still holding UAL miles I would immediately demand paper ticketed awards from UAL on Delta for cities I knew I would travel between in the next year. The worst that might happen is that I'd get stuck with a $50 change fee for changing dates.