I had my seats changed within the 24 hr check in window. As I often do the last week before departure on long flights to Asia, I check my seats often to judge if my E+ row had space next to me.

On one occasion UA changed not only my seats but also my connection. I think they meant well, but the change included a middle seat on.a route that would have brought me up short for reaching Premier Executive and the year was almost over. I had to scramble to get everything corrected as I couldn't do anything online within the 24 hr window. Took 4 phone calls and much time.